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VOL. VI WINTER 1961 

Remarks at the Dedication of wn Neumann HalL _____ - _ _ _ 1 

The Association Factor in Information Retrieval _________ -

H. EDMUND STILES 7 

Introduction to. Cryptology-IV __ ---------------------- WILLIAM F. FroEDMAN 25 

Pattem Recognition ______________ -- _ - ____ - ____ -- _ -- __ -

WALTER W. JACOBS 17 

CONFIDENTIAL 
CO~UIOHHIAL 

THE NSA TECHNICAL JOURNAL 

EDITORIAL POLICY BOARD 

S. KULLBACK, Chairman 

WILLIAM A. BLANKINSHIP ARTHUR F. MATHISEN, Sec. Advisor 

LAMBROS D. CALLIMAHOS IGNATIUS G. MATTINGLY, Exec. Sec'y 

HOWARD H. CAMPAIGNE HAROLD J. STUKEY 

DANIEL M. DRIBIN COL. M. J. BARTOSIK 

PAUL F. FRIEDMANN WILLIAM D. WRAY 

EDITORIAL STAFF 

EXECUTIVE EDITOR 

PAUL F. FRIEDMANN 

PANEL OF EDITORS 

LAMBROS D. CALLIMAHOS, Chairman 

JOSEPH BLUM 

GEORGE L. CHESNUT 

MORTON KUPPERMAN 

EDWIN C. FISHEL 

LOWELL K. FRAZER 

FRANK W. LEWIS 

CHARLES W. RECHENBACH 

C. RUSSELL SUMMERS 

NOTICE: This material contains information affecting the National Defense of 

the United States within the meaning of the Espionage Laws, Title 18, U. S. C., 

Sections 793 and 794, the transmission or the revelation of which in any manner 

to an unauthorized person is prohibited by law. 

The NSA Technical Journal is published four times a year under the direction 

of the NSA Technical Journal Editorial Policy Board. Telephone: OUTSIDE: 

7249, SECURE: 3057. Any cleared and indoctrinated person may be permitted 

access to the Journal by a regular receiver of the Journal, or by the Library. 

Copies of the Journal which are no longer required may be destroyed, and the 

accompanying certificate of destruction filled out and returned to the Office of 

Administrative Services. 

NSAL--8-129,098 

Use of funds for printing this publication approved by the Director of the 

Bureau of the Budget, 20 January 1960. 

COt~Flf'El'4'flAL 
Extending the Challenge 

REF ID:A62856 

co~mDDHIAL 

We and our customers are continually involved in evaluating the 

two most significant aspects of COMSEC systems-security and 

logistics. Singly or in combination they present a fascinating challenge for devising the means to facilitate reaching rational decisions 

which provide the best over-all balance. Despite our efforts there is 

still no formula, no clear-cut criteria for weighing the associated 

variables. The implications of a wrong "guess" are shattering in 

terms of impact on our national security. Dozens of parallel 

examples could be cited for SIGINT. 

While the activities of the Agency continue to mushroom in 

complexity, it is important that our approaches to problems keep pace. 

There is within our grasp the essence of a solution. It is no accident 

that we have engaged in some operations research, applying our 

"cryptologic" talents in statistics, mathematics, and engineering to 

what are actually "management" problems. The very fact that our 

in-house scientific skills can be blended to analyze a "cryptologicmanagement" question holds promise of possibilities and hope. 

The cryptologist-manager of tomorrow must acquire system and 

discipline needed for sound planning; but he has not yet learned how 

to judge problems in all the necessary dimensions, to establish a 

balance, and to decide things not on intuition alone, but on a sounder 

more scientific base. 

What we lack is a way to treat with assurance typical situations 

which require that the solution to the "flap" be melded with the needs 

of the future; that our capabilities project the demands of our 

customers; and that individual readjustments not threaten the Agency 

as a whole or any of its missions. This will be possible only through 

the use of a logical structure which provides definitions, specifications, 

measurements, and a common communications medium. 

We are lucky that cryptology and management are both infants as 

professions and as sciences. There may be likenesses in their individual, general methodologies, some possibility of a harmonizing 

logic. A common, symbolic, cryptologic language is beginning to 

emerge. The stimulating analogy is that the management language 

is headed toward a similar integrated and synthesized structure! 

Further, it could become complicated by moral and social considerations. 

Guest Editor for this issue is Mr. Paul E. Neff, Assistant Director NSA for 

Communications Security. 

co~mDDHIAL 
REF ID:A62856 

-CO~mBEt~flAt" 

The cryptologic skills, problems, and needs we have today offer a 

fabulous opportunity to experiment more fully in the management 

area; and the possibilities :fire the imagination. 

CORRECTION 

In the July-October 1960 issue of The Journal, Dr. A. Sinkov was 

erroneously referred to as Assistant Director of PROD, NSA. 

Dr. Sinkov's correct title is Deputy Director, PROD, National 

Security Agency. 

ii 
REF ID:A62856 

UNCLASSIFIED 

Remarks at the Dedication of 

John von Neumann Hall 

Unclassified 

A new building to house the NSA Research Institute was dedicated on 

October 22, 1960 at Princeton University. The major dedication addresses were delivered by Dr. James R. Killian, Jr., Chairman of the 

Board, Massachusetts Institute of Technology, and Dr. Robert Francis 

Goheen, President of Princeton. The addresses are reproduced here with 

introductory remarks by Dr. Howard H. Campaigne, Chief, Office of Research, NSA. 

The Institute for Defense Analyses (IDA) is a non-profit organization which was founded in 1956 by five of the leading research institutions in our country: Massachusetts Institute of Technology, 

Tulane University, California Institute of Technology, Case Institute 

of Technology and Stanford University. It has one broad purposeto carry out research on problems referred to it by the Defense 

establishment. 

Two years later, the Baker Committee proposed that a separate 

research facility be established, preferably in an atmosphere conducive to intellectual endeavor. The NSA Scientific Advisory Board, 

of which Professor von Neumann of Princeton was a member, strongly 

endorsed the concept. The recommendation was taken to the White 

House. 

President Eisenhower approved the establishment of an activity to 

perform independent cryptologic research in February of 1958 and 

the search for a suitable location was underway. Among the groups 

approached were Syracuse University (with the possible help of 

General Electric), The Rand Corporation, IBM (with Stanford 

University), Harvard University, Princeton University and, of course 

IDA. 

IDA undertook the project. It immediately set up a new division, 

the NSA Research Institute (also known as Focus), to do the work 

and entered into a contract with Princeton for a new building to house 

the effort. It is the dedication of this building which was the occasion of the following speeches. 

Dr. J. R. Killian, Jr . .. 

I speak in behalf of President Norton, the trustees and staff of the 

Institute for Defense Analyses in expressing appreciation and satis1 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED VON NEUMANN HALL DEDICATION 

faction in the splendid opportunities and facilities provided by 

Princeton University for the work of the Institute's Communications 

Research Division. We are especially proud and grateful that the 

University has made it possible to have this fine new building available for the Institute's communications research program and that it 

has been possible for us to join with the University in making this 

building a memorial to Dr. John von Neumann. Because of his great 

accomplishments as a mathematician and his remarkable contributions to the public service of his adopted country, it seems happily 

appropriate that this building have the distinction of his name. 

From the standpoint of the Institute for Defense Analyses, this 

whole enterprise here in Princeton has been a happy undertaking. 

The arrangements entered into with the University for bringing the 

building into being have worked well. We have welcomed, too, the 

opportunity to join with Princeton in planning for the design and use 

of the computer, one of the facilities housed in the building. We are 

glad that the University community has access to this fast and versatile computer and that other parts of the program managed by 

IDA here have been so arranged as to permit a fruitful relationship 

between the Communications Division and the scholarly community. 

This is possible because a part of the work of IDA's Communications Division is in fundamental areas of mathematics and associated 

communications sciences, which are suited to university participation. 

I speak for President Norton and Dr. Rosser and their associates in 

expressing our appreciation to the University and the University 

community for their very great contribution in working out these 

collaborative arrangements. 

IDA has another reason for being happy with the choice of 

Princeton's hospitality: I refer to the exceptional resources in mathematics, perhaps unexcelled in the world, which are concentrated here 

in the University and in the Princeton community. Altogether we 

feel the auspices to be particularly benign for our undertakings here. 

Woodrow Wilson once observed that "Government is not a machine, but a living thing. It falls, not under the theory of the universe, but under the organic life. It is accountable to Darwin, not 

to Newton." The Institute for Defense Analyses represents a small 

organic extension of Government-a mutation which provides new 

opportunities for our Government to draw upon the resources of the 

nation's academic and scientific communities in a way accountable 

both to Newton and to Darwin and that is beneficial to these communities as well as to the Federal Government. Since the war we 

have seen many ingenious methods devised in the area of what Don 

Price has called "federalism by contract" which have served to make 

available to national policy making and the national Government 

UNCLASSIFIED 2 
REF ID:A62856 

VON NEUMANN HALL DEDICATION UNCLASSIFIED 

advisory services otherwise not easily accessible. This enterprise 

here in Princeton represents one of these novel and, we venture to 

hope, mutually beneficial arrangements which brings a new element 

of strength to our national life. 

President Goheen, we are happy and privileged to be in this university community and to have the cooperation of your institution 

and your colleagues. 

Dr. Robert F. Goheen ... 

Our gathering this morning, widespread though we are in the 

institutions we represent and diverse perhaps in our interests, brings 

us together to pay honor in common to the memory and influence of 

a rare individual. 

Three decades ago John von Neumann, at the age of 26, accepted 

Princeton University's invitation to join its faculty as professor of 

mathematical physics. A very few years later (1933), when the 

Institute of Advanced Study was brought into being, he was appointed 

one of its founding professors. Thereafter, whether here in Princeton 

or commuting to Los Alamos or Santa Monica, or serving with scientific commissions, or temporarily making his home in Washington, 

Professor von Neumann considered himself a Princetonian and loved 

the ways of life that are the hallmarks of this academic community. 

All of us here are deeply aware of Professor von Neumann's scientific legacy, of his salient contributions to man's knowledge, of his 

devotion to the principles by which free men live. We who are 

Princetonians recall with especial pride the honors that rightfully 

came to him: The medal for Merit in 1947; the Medal of Freedom in 

1956; and the Enrico Fermi Award,-the citation attending the last 

rightly stressed that he more than anyone else foresaw the important 

and necessary role which high-speed computing machines would play, 

not only in the control and use of atomic energy but also in the 

general advancement of the sciences. 

The vital influence he exerted in all that he did was expressed 

wonderfully well in the dismal February of 1957 by one of his close 

friends and associates who is with us today, Dr. Robert Oppenheimer: 

"To his many friends, his students, his colleagues, John von Neumann 

was the highest and liveliest intelligence they were ever to encounter. 

A mathematician of immense scope and power, he contributed to many 

fields of learning and created others. He was a masterful abstract 

analyst, with an unparalleled sense for practical invention, so that he 

enriched learning and practice equally. His sober and often melancholy realism was tempered by great warmth and generosity. We 

know no one like him." 

3 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED VON NEUMANN HALL DEDICATION 

Recollections of this outstanding man of science, who could recite 

Faust from memory and whose outreach was immense, have become 

a kind of living legend in our community. For myself, I especially 

enjoy an anecdote which I first got from a colleague but later saw 

repeated in a published tribute. 

One evening at the von Neumanns' Westcott Road home, so the 

story goes, Professor von Neumann and an eminent Byzantinist were 

discussing a little-explored corner of history and came to argument 

over a date. The historian said it was this; von Neumann insisted it 

was that. Eventually, as scholars should, they looked it up, and von 

Neumann was right. Some time later, when again invited to the 

von Neumann house, the historian is said to have said: "I'll come if 

Johnny promises not to discuss Byzantine history. Everybody 

thinks I am the world's greatest expert in it, and I want them to keep 

on thinking so". 

It was fifteen years ago that this warm, many-sided individual, 

anticipated the creation of an organization to serve purposes such as 

The Institute for Defense Analyses now serves. In a memorandum 

dated September 5, 1945-in which he was analyzing the one highprecision electronic machine then approaching completion-he wrote: 

"There are many important problems in hydrodynamics, aerodynamics, celestial mechanics, and in various other fields, which are 

practically inaccessible to the present methods of abstract mathematical 

analysis, and for which the capacity of human computing machines, or 

of existing, non-electronic computing machines, is absolutely inadequate. These problems can only be dealt with by machines which 

possess intrinsic speeds that can only be reached by electronic procedures. Such speeds render any intelligent human intervention, while 

the machine is working, impossible, and therefore they necessitate a 

complete automation of the device." 

He went on to suggest that the construction and operation of an "allpurpose machine" should be undertaken immediately by a purely 

scientific organization, as opposed to existing governmental or industrial agencies. He emphasized the desirability of planning "without 

any inhibitions," for free operation governed principally by scientific 

considerations. 

So also, writing three days after the Japanese surrender, Professor 

von Neumann urged that "the Government needs the help of a scientific institution" for these purposes, and he foresaw the creation of 

some future, central postwar research agency that might well be 

economically self-supporting. Again he cautioned that its independence and ability to exert a directing influence on future developments were matters of vital concern. 

This morning-an even decade and a half after Professor von 

Neumann, peering into the future, suggested this kind of charter for 

UNCLASSIFIED 4 
VON NEUMANN HALL DEDICATION UNCLASSIFIED 

what is now the Institute for Defense Analyses-we sit, as it were, 

before the translation into reality of some significant part of his 

vision. And I find myself greatly moved by the devotion and respect 

which are apparent in this gathering-devotion and respect for the 

man whose memory we honor, devotion and respect for those qualities 

of mind and character which he displayed in his all too short lifetime, 

and of which the Institute for Defense Analyses, with its demonstrated 

achievements and its rich promise for the future, is such an appropriate expression. 

5 UNCLASSIFIED 
} 

UNCLASSIFIED 

Pattern Recognition 

BY WALTER W. JACOBS 

Unclassified 

The broad class of pattern recognition problems is considered, and the 

example of handwritten signatures is used to elucidate the general problem. A model is presented which shows the relation of pattern recognition to communications, and the structure of recognition procedures is 

discussed. 

Human sensory perception seems to involve pattern recognition in 

a fundamental way. When we examine the physiological processes 

involved in the perception of shapes and colors, sounds, textures, and 

so on, we find that in these processes there are large numbers of receptor elements affected by any stimulus. Starting with the arrangement of the affected elements, the brain arrives at an appropriate image, although we have little knowledge of how this is accomplished. 

Webster's New International Dictionary defines pattern as " ... an 

arrangement of parts, elements or details that suggests a design or 

orderly distribution." A definition that is closer to our requirements 

is: a design or orderly structure that underlies an arrangement of 

parts, elements or details. To recognize a pattern is to detect or 

identify the structure associated with the particular arrangement or 

occurrence. 

The term "pattern recognition" is sometimes restricted to refer to 

the identification of shapes. We are using it in a broader sense, to 

include, for example, speech recognition and even such other problems as identifying a piece of music, a poem, a face or a voice. 

In speeding up the processing of information, the mechanical recognition of patterns is becoming increasingly necessary. Various 

forms of this problem are being worked on. In order to provide a 

firmer foundation for such work, a model of the general recognition 

problem is presented here; this model is explicit enough to provide a 

formulation for mechanical recognition, and at the same time it appears broad enough to encompass human recognition. 

The principal aim of such a model is to indicate the conditions 

that should be satisfied if a successful recognition procedure is to be 

achieved. Thus it provides a basis for evaluating partial attacks on 

the problem. 

7 UNCLASSIFIED 
UNCLASSIFIED PATTERN RECOGNITION 

THE PROBLEM OF SIGNATURE RECOGNITION 

The exposition will be organized around a specific example-the 

mechanical recognition of a handwritten name. The example has 

been chosen because of its concrete nature, and because it is extremely familiar to everyone. 

In recognizing a signature, we may be trying to answer one of a 

number of possible questions. What is the name of the signer? 

Does the signature correspond to the standard for a checking account in a particular bank? Is it a valid or a forged signature? 

Each of these questions gives rise to a different recognition problem, 

and it should be clear that the corresponding procedures need have 

little or nothing in common. It is necessary to be very explicit 

about the problem to be solved in order to avoid tackling too much 

or accomplishing too little. 

The discussion will deal with the first of these questions: identifying the name. It is assumed that the only information available for 

the problem consists of two lists, one containing 250 first names, and 

the other 4,000 surnames. (We suppose, to eliminate a complication 

that would add nothing to the exposition, that there is no middle 

initial.) No standard signature, such as would exist in the bank 

problem, is provided. 

The objective in discussing this problem is to illustrate and illuminate the general situation. For present purposes, it is of little concern whether this form of the problem is of practical interest, or 

whether the approach to be described is feasible. 

THE COMMUNICATION MODEL OF PATTERN RECOGNITION 

Our model is based on an analogy between the usual communication situation and the pattern recognition problem. In communication, we deal with messages, sent and received. The original message is converted to a signal or other physical form and is transmitted along some communication channel. The channel is in general 

"noisy'', and the signal is distorted or modified. It is then received 

and recorded, further degradation of the signal occurring in the process, and the resulting record is used to obtain information about the 

original message. By interpreting "message", "signal" and "record" 

in a somewhat more general sense, we can identify these same elements in pattern recognition. 

In communications, the origination and transmission of the message are usually intentional; in pattern recognition, however, this is 

too restrictive. The criminal who leaves his fingerprints at the 

scene of his crime is unwittingly sending a message to the detective. 

To the latter, the identity of the criminal corresponds to the pattern 

underlying the fingerprints. 

UNCLASSIFIED 8 
REF ID:A62856 

W.W. JACOBS UNCLASSIFIED 

Similarly, in the signature problem, the individual writing his name 

is originating a message. The light reflected by the signature plays 

the role of the signal, and the receiving element may be the retina of 

the eye or the photosensitive component of a mechanical scanning 

device. In the form of the problem being discussed, the name is the 

desired pattern. 

These two examples illustrate what is meant by "pattern" in 

general. A particular pattern, such as the.name "John Smith", can 

be represented by many different messages; not only can the signer 

vary the size and form of his signature, but also there may be different people writing the name. However, in the situation being discussed, all possible signatures fall into (250) (4,000) + 1 = 1,000,001 

different classes, corresponding to the possible pairs of names on the 

given lists or to the additional case- the "null pattern" -when one 

or both names are not listed (or perhaps what is being examined is 

not even a signature). 

Because handwriting is often bad, and because "noise" further obscures what is written, no recognition procedure can be uniformly 

successful in assigning a record to its pattern. It takes only a smudge 

to make "Jean" practically indistinguishable from "Joan", or "South" 

from "Smith". What the procedure can do is divide up the set of 

possible records into classes or categories, each class corresponding 

to a single pattern. For example, one such class would contain 

every record which is assigned to "John Smith". This dividing up 

should be done so as to minimize the effect of incorrect recognition. 1 

Some writers have used this dividing up of the set of records into 

classes as the basis for a definition of pattern. It becomes "that 

property which all the records of a single class have in common." 

The definition is unsatisfactory, and involves a confusion between 

the recognition procedure, on the one hand, and the success with 

which a given mechanism achieves the intended assignment of records to classes, on the other. This becomes clearer when it is 

realized that the definition excludes any notion of pattern structure, a 

term which encompasses all the knowledge about the patterns which 

is not present in the totality of records. As the example will show, 

it is this external knowledge on which a recognition procedure is 

based. 

MESSAGE, SIGNAL AND RECORD 

To look at a communication situation and to specify the place 

where the message is in existence and entering the transmission proc1 Procedures which allow for more categories of records than there are patterns may be required if, under appropriate conditions, an indecisive outcome is 

desirable. This involves additional considerations, and is not discussed further, 

although the present treatment can readily be modified to handle it. 

9 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

:ir ij!I di )1'11iiii :1f! t;i !i ! 'I:,·': 1, I ~·I i!! 1'..i l!Ji'} !!1' Ulli!ii 

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'iHi·,1i' • • • ' I~~· ;;> -:+ Figure la shows the signature "John Smith" in the form which is assumed available for 1

:: •'•• 

~ill the recognition problem discussed in the text. This consists of a written name on a document=~ 

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UNCLASSIFIED 10 
This indicates tl.e type of record wliich miglit be produced by an optical scanning mechanism. The ''.;:Jgjfffi:J:!!JBJ~ 

field on which the signotu"' appears would be considered as made up of small squares, In tl.e output ':':.. 

of the scanner the corresponding square would be conside"'d "block" if the inked area of the field squarer:;':tl' rt::i±m-±±±::±i±t±:::±l 

exceeded a specified threshold, and would be considered "white" if it did not. l~il'1Illi.HE:!HH±±fil!l3 

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REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

ess, often calls for an arbitrary choice. One may say that transmission commences with the conversion of a written message to 

electrical form; it is just as reasonable to say that it begins with the 

conversion of a mental message to verbal or written form. 

The same kind of choice arises in recognition situations, and one 

can be somewhat free in specifying the point at which the message 

exists and the dynamic process which constitutes the signal has 

begun. The signal intervenes physically between the originator and 

the recipient, and the form of signal available to the latter depends 

on his relative location and other conditions. In the class of recognition problems represented by a given procedure, it is useful to 

think of reception conditions as relatively fixed. 

In the example of the handwritten name, the usual physical effect 

will be a piece of paper or cardboard containing the writing. This 

may be called the "static" signature (Fig. la), and this is the kind of 

signal which will be considered in the discussion here. If the conditions of the problem permitted us to observe the act of signing, then 

the signal would more properly be regarded as the timed succession 

of pen positions, as indicated in Fig. lb. The two problems are evidently different, although the same pattern is to be recognized. A 

recognition procedure based on the second type of signal could make 

use of knowledge (about the succession and direction of strokes, for 

example) which is not directly available with the static signature. 2 

Before a recognition procedure can be applied to the signal, it 

must first be received and transcribed. The resulting record is the 

input to the procedure, and summarizes all of the information that 

applies to the particular occurrence of the problem. Information 

about the pattern structure-such knowledge as the fact that names 

are produced by continuously-drawn strokes, and that they consist 

of letters in pronounceable combinations-is not present in the record, but is collateral to it. 

Figure 2 shows a record of the signature such as might result from 

scanning the signal with a facsimile device. The form of the record 

is chosen by the recognizer, within the limitations imposed on him by 

his access to the signal and the technical devices available to him. 

The signal itself is a physical phenomenon which he cannot control. 

2 After the present paper was written, the author was shown an unpublished 

manuscript, "Machine Reading of Handwriting", by L. S. Frishkopf and L. D. 

Harmon of Bell Telephone Laboratories, which discussed a proposed machine 

procedure for recognizing handwritten material from the time plot of its x and 

y coordinates. The approach is an excellent illustration of the general class of 

procedures described here. 

UNCLASSIFIED 12 
1 

! 

REF ID:A62856 

W.W. JACOBS UNCLASSIFIED 

VARIATION, NOISE AND PROBABILITY CONSIDERATIONS 

An individual will produce many versions of his signature, reflecting such sources of variation as space available, muscular control, 

and so on. With upwards of 100,000,000 Americans who can write, 

producing dozens of possible signatures each, the number of different 

messages in our problem is in the billions. These are grouped, by 

the task set, into 1,000,001 patterns. The differences among the 

messages in a pattern class constitute the variation. 

When John Smith undertakes to produce an instance of his signature, a particular message in the pattern corresponding to his name 

is originated. However, the actual signal is not uniquely determined 

by that message because of noise. The table on which he is writing 

may shake, the ink may blot or smudge, and dirt or moisture may 

further alter the written form of the signature before it reaches the 

recognition process. 

The act of producing the record itself will introduce more noise to 

obscure the information present. The effect which results from the 

discrete field of the scanner is graphically shown in Fig. 2; however, 

noise is inevitable in any device, whether it operates discretely or 

continuously. 

Because of the intervention of variation and noise, it cannot be 

assumed that every record can be unambiguously assigned to one and 

only one pattern. As has already been pointed out, we frequently 

encounter cases where even the human recognition procedure fails to 

obtain a decisive answer. Our model assumes that every pattern 

gives rise to a definite probability distribution over the set of possible 

records. 3 

The recognition procedure must take account of the probability 

distributions for the various patterns. Often these will not be given 

a priori, but must be estimated on the basis of samples of records for 

which the corresponding patterns are known. 

The general recognition problem, in terms of the model which has 

been presented, is therefore seen to fall into the well-known category 

of statistical problems in which we have a single sample drawn from 

one of a finite set of populations, and wish to "estimate" the population from which it originated. There are, therefore, two distinct 

aspects to any recognition procedure: one concerned with the statistical decision that must be made, and the other involved with the 

means of transcribing the original signal and of physically carrying 

out on the resulting record the statistical calculations that are necessary. 

3 AB discussed in the Appendix, this assumption appears to be necessary in 

order that the recognition problem be well-defined. 

13 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

THE STRUCTURE OF THE RECOGNITION PROCEDURE 

When there are many patterns, or when there is a considerable 

amount of variation within the individual patterns-in other words, 

whenever the number of possible messages is very large-the statistical rules that would assign each record to its appropriate pattern 

are too complex to carry out in a single step. In this case, the 

recognition procedure is more appropriately considered as a series of 

operations. 

There are four well-marked functions or aspects in recognition, 

and we call them Representation, Extraction, Classification, and 

Integration. They are indicated in the flow-chart of Fig. 3. These 

aspects appear to be necessary in any non-trivial problem, and one 

can use them to appraise the extent of progress that is made in any 

practical proposal for a mechanical recognition device. 

If the published material on character recognition and other problems is evaluated on this basis, in most cases it appears that only a 

part (and often the easier part) of the recognition procedure has 

actually been attacked. Only where variation and noise can be rigidly controlled-as in examples of character recognition where the 

method of printing is precisely specified-has much headway been 

made, and even in these relatively simpler problems the procedures 

described appear to contain some serious gaps. 

The four aspects are discussed in turn in what follows. The logical flow-chart of Fig. 3 is not intended to indicate a corresponding 

physical separation of function in an actual device; it is quite possible that in a particular procedure a single mechanism could effectively combine two or more functions. 

REPRESENTATION 

The determination of the method of recording the signal constitutes the first aspect of the recognition procedure. This step is 

called representation, and it may also be thought of as selecting the 

form of the record. 

This same first stage exists in human recognition. The perception of a shape, for example, commences with the stimulation of 

certain of the discrete array of receptor cells in the retina of the eye. 

We have already seen that representation introduces noise. The 

signal-to-noise ratio may be increased within limits by increasing the 

faithfulness of the recorder. In Fig. 2, if the field being scanned 

were divided into a larger number of cells, the record would more 

closely approximate the signature. 

It is possible to incorporate a noise "filter" or "suppressor" into 

a recording device, but this merely combines with the representation 

stage a function that properly should be considered part of a later 

UNCLASSIFIED 14 
t 

I 

i 

REPRESENTATION 

1---, 

I I EXTRACTION 

I 

I 

I 

I 

I 

I 

I CLASSIFICATION 

I 

I 

I 

I 

I 

I 

j INTEGRATION 

I 

L- _ _J 

REF ID:A62856 

w. w. JACOBS UNCLASSIFIED 

Figure 3 

Structure of the General Recognition 

Procedure 

This flow-chart indicates the functional nature of 

the recognition procedure rather than the organization 

of physical components of a recognition device. The 

rectangles represent aspects or functions of the procedure, the circles inputs and outputs. The dashed 

line suggests the iterative or sequential approach which 

is described. 

15 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

section of the recognition procedure. Paradoxically, the recognition 

procedure can sometimes be simplified by using an extremely coarse 

scan, thereby passing up much of the information available in the 

effect. Here again the representation stage is being combined with 

later parts of the recognition procedure. 

It is useful to discuss the informational aspect of the problem 

somewhat further. Because 1,000,001 is approximately 22°, a signature which has been correctly assigned to its pattern-i. e., has had 

its name identified-has contributed about 20 bits of information 

relevant to the name identification. It contains far more information than this, some of which would be relevant to other problems. 

The use of pattern structure and its implied redundancy makes it 

possible to discard much of the additional information. However, 

the function of discarding information should be kept conceptually 

distinct from the function of representing it, even though a single 

physical device may simultaneously perform both functions. 

EXTRACTION 

The remainder of the recognition procedure operates on the record 

as input, and yields an estimate of the underlying pattern. While it 

is theoretically valid to consider this estimate as a statistic calculated 

from the record by a single mathematical operation, in practice it is 

often important to break down the process. 

The estimation of the pattern from the record begins with a function that may be called extraction. We will first consider what this 

involves, and then indicate some of the difficulties associated with 

carrying it out. Extraction consists of selecting a part of the record, or segment, in such a way as to reduce or eliminate the effect of 

a source of variation in the original set of messages. There are two 

distinct ways in which this can take place. The segment may correspond to a group of patterns so chosen that some variation is cancelled out; such a group is called a subpattern. For example, if all 

patterns are grouped according to the first name, and the segment 

includes only the corresponding part of the record, then the subpatterns are the first names. In this partial problem there is much less 

variation than in the full problem involving a single complete pattern. The reduction is much greater if the segment includes only 

that part of the record corresponding to the initial letter. 

The second type of extraction aims at counteracting variation 

within the pattern classes by selecting parts of the record that correspond to some standard or canonical feature of the entire class. 

Adjustments for variations in size, registration or orientation of the 

record are of this type. 

UNCLASSIFIED 16 
.... 

-.;J 

c 

z 

('\ 

r-

> 

~ :;; 

rn 

c 

,, 

~ 

~ 

1111 

11 1 

1 1 

1 11 

1 1 

1 11 

1 1 1 1 

11 

11 

11 

1 

11 

111 

1111 

1111 

1 111 1 11 11 

11111 llll 1111111 

11 

1 

11 

11 

11 

1 1 

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1 1 1 

11 

11 

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1 

11 

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11 111 

11 111111 

l l 11 

11 l :1( 1 11 

1 11 11 11 11 11 

11' 11111111111111111111 

11111/11111 111 11 

1 1111 1 11 111 111 1 1 11 1 llllllllllll ll 1 

1111 llll 11 111 11 11 1 1 11 l ll 11 ~l lll 

111 

11 

1111 

11 1 

1 1 1 

111 

1 

1 

11 1 1 1111 11 1111 

Figure 4 Record Matrix With Letter Separations Indicated 

The black squares of the record of Figure 2 ore here represented by "1 ", and the white squares are 

represented by a blank space. The lines in the figure divide up the 1 's into groups which correspond 

opproximately to the individual letters al the name. 

11 

1 

c 

z 

('\ 

r-

> V> 

~ 

::!! 

rn 

c 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

The term "segmentation" is frequently used for the first type of 

extraction. However, it seems desirable to replace this term, both 

because it does not fit the second type, and because it seems to imply 

that the entire record is divided up into segments at one stroke; this 

latter restriction is unnecessary. 

Extraction is often a troublesome stage, especially if it is done in 

the form of complete segmentation. Some of the reasons for this 

are exemplified in Fig. 4, which shows the record of Fig. 2 (expressed 

as a matrix of O's and l's with the O's suppressed for clarity). 

In the figure, the approximate segmentation into letters is indicated by lines. 4 But the matrix, although set out in a rectangle, 

will as a practical matter be read linearly, and most probably either 

by rows or by columns. Thus, the segments will not in general be 

connected pieces of this linearly described record. Either the extraction rule must be a complicated one, or the segments will not correspond perfectly to single letters. 

There are other problems in extraction besides non-linearity. The 

segments are not usually independent, because the way a letter is 

written will depend on what its neighbors are. Also, there is frequently an intrinsic ambiguity characteristic of handwriting, which 

is illustrated in deciding where to terminate the second letter of the 

second name: is this an i or r, nor u, or m? 

The kinds of difficulty pointed out here can arise in many recognition problems. In trying to avoid these difficulties, the attempt is 

sometimes made to dispense with extraction and work with the record as a whole. However, except in rather trivial cases, at least the 

second type of extraction is still necessary-and because this may 

involve a less specific kind of pattern structure, it may be no easier 

to handle properly. 

Consider, for example, a variation of the signature problem in 

which a file of standard signatures is available for comparison. One 

can conceive of an approach which matches the record as a whole 

against each standard. In order to do this successfully, the matching process must relate corresponding parts of the record and the 

standard. But parts of a signature vary in their relationship to each 

other; in comparing signatures by eye, we find it necessary to adjust 

for differences in spacing or size which interfere with any simple 

basis for comparison. Thus, extraction is still required to make the 

parts of the record correspond to those of the standard. 

• As an instance of the puzzles of human perception, the reader should note 

how much more easily the name may be recognized from the record as shown in 

Fig. 2 than from the informationally equivalent form in Fig. 4. 

UNCLASSIFIED 18 
REF ID:A62856 

W.W. JACOBS UNCLASSIFIED 

In the experimental stage of developing such a procedure, a correlation technique relying on the presence of "above-the-line" letters 

(b, d, f, h, k, 1, t) and "below-the-line" letters (f, g, j, p, q, y, z) 

might be tried. The extraction might involve location and scale adjustments of the record so as to produce coincidence at both the 

beginning points and ending points of the observed and standard 

signatures. However, writing does not always space its letters uniformly, and we can therefore conclude that the indicated approach 

would have a higher probability of error than could be attained with 

a more sophisticated extraction. Whether the errors could be tolerated in order to keep the procedure simple would depend on the 

specific circumstances of the actual application. 5 

Let us return to the signature problem which we have been using 

as an example, and use it to emphasize an important point about 

subpatterns. These are not predetermined by the structure of the 

patterns, but are selected in the course of developing an efficient 

recognition procedure. In the signature problem names are composed of letters, and letters of strokes, but this fact does not compel 

us to use letters or strokes as our subpatterns. 

A relatively simple way to start the process would be to extract 

as a segment the part of the record that corresponds to the initial 

letter of the first name. However, the underlying subpattem would 

be not the letter itself, but a properly chosen group of letters. One 

such group might be the letters which as capitals have a loop below 

the line: J, Y, Z. 6 

In summary, extraction operates on the record and produces a 

segment, in such a way as to offset a substantial part of the variation 

present among the original set of possible messages. It may do this 

by standardizing, so that the resulting segment still is used to estimate the entire pattern. Alternatively, the segment may relate to a 

subpattern of the original pattern. 

CLASSIFICATION 

The determination of the estimated subpattern from a segment of 

the record is called classification; it constitutes the third aspect of the 

recognition procedure. It differs from the problem of estimating the 

entire pattern from the record in only one respect: that no further 

extraction takes place. At this stage a manageable piece of the 

6 A typical "practical" solution might be to weight the errors in favor of rejection, and use human inspection of the rejects. Since the back-up inspection 

is part of the "mechanical" recognition procedure, this solution might turn out 

to be much more expensive to operate (although much cheaper and quicker to 

develop!) than a more sophisticated machine. 

6 How to continue from this start is discussed below under integration. 

19 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

original problem has been cleaned up. The input may be thought 

of as an observed vector (or a continuous counterpart); the result of 

the classification is an estimate of the subpattern. 7 

In order to determine how a machine is to carry out the classification aspect of a recognition procedure, two interrelated tasks must 

be accomplished. The first task is to decide which subpattern each 

possible segment should be assigned to; and the second is to produce 

a mechanism or calculation which actually accomplishes or sufficiently approximates the desired assignment. The principal consideration in handling the first task is the risk associated with erroneous 

assignments; in the second task, the practicality of the assignment 

procedure. 

We referred earlier to the literature on pattern recognition problems. The partial attacks we mentioned are largely concerned with 

classification, and within this area primarily with the carrying out of 

a specified assignment function. 8 Relatively few writers give any 

recognition at all to the task of choosing the assignment function. 

In some cases this seems to stem from the view that it is someone 

else's job to eliminate (in our terminology) all of the noise that exists 

in the channels of communication, for in the absence of noise the 

correct assignment is presumably known. 

The determination of a suitable assignment function is analogous 

to the standard statistical problem of developing a test of hypotheses. 

The segments of the records are analogous to vector samples, and the 

subpatrerns correspond to the statistical universes from which the 

samples are drawn. In our example, the subpatterns for the initial 

segment are groups of capital letters, such as the group (J, Y, Z); 

and an additional one, the "null" subpattern, corresponding to the 

case where no underlying letter is present, for example, because the 

extraction was incorrectly done. 

The methods of deriving suitable statistics for the classification 

problem belong to decision theory. In order for these methods to be 

applied, however, two assumptions must hold. These assumptions 

are: first, that each subpattern gives rise to a valid probability dis7 It can be questioned whether this oversimplifies the situation; might not 

the proper output be a set of probabilities or other scores assigned to the various 

subpatterns? Such a modification is not necessary, but to explain the justification for this assertion, a long and difficult philosophical and mathematical digression would be required. In any case, those who prefer may interpret "estimated subpattem" as a vector of posterior probabilities; nothing essential in 

the remaining discussion is affected. 

s The Perceptron research, and related investigations, treat the problem of 

learning an assignment function from a sample of assignments. The pre-existence of the function, in implicit form at least, is apparently assumed. 

UNCLASSIFIED 20 
W.W. JACOBS 

REF ID:A62856 

UNCLASSIFIED 

tribution of the corresponding segments; second, that either the 

knowledge of pattern structure yields complete specifications of these 

distributions or there are available adequate samples to estimate any 

unknown parameters. 

The importance of these assumptions is underlined by the fact 

that many attempts to develop recognition procedures are carried 

out under laboratory conditions, with noise kept to a minimum. The 

result is that no information is obtained about the probability distributions that hold under actual conditions, and the procedures that 

apply in the laboratory may be of little use outside. 

It is sometimes claimed that the question of a proper statistic for 

classification is not important: that there exists some transformation 

of the segment which will expose an invariant, easily identified characteristic of the subpattern. This assumption has generally proved 

too optimistic even in such relatively favorable situations as the 

recognition of characters from a fixed font. In the case of written 

letters, even the human will make some proportion of bad identifications without the help of context to correct him. In our handwriting example, it is evident from Fig. 4 that once the letter "n" 

has been isolated, there can be no test which clearly .differentiates it 

from the letter "u". However, as soon as it is admitted that no 

perfect test can exist, it becomes important to specify one that keeps 

down the probability of error. 

It should not be assumed, because we have said that methods 

exist for the determination of classification statistics when the proper 

assumptions are satisfied, that the task is always a trivial one. Even 

when the number of subpatterns is as small as three, the theoretical 

difficulties can be severe and the practical ones are worse, unless the 

subpatterns have been well chosen. As the number of subpatterns 

becomes large, the difficulties become overwhelming. This may help 

to account for the almost universal hope in such cases that some 

panacea will, by great good luck, do an adequate job. 

Trying to avoid extraction by working with the record as a whole, 

one has to find a method of classification with large numbers of underlying patterns. All of our experience supports the conclusion 

that most of the time it is better to break a problem into smaller 

parts than to struggle with the undivided problem. 

With our handwriting example, we shall prudently avoid any discussion of possible classification statistics. For the purposes of the 

rest of the discussion, we assume that such a statistic has been applied, and has produced an estimated subpattern for the initial 

segment. 

21 UNCLASSIFIED 

Ii I, 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

INTEGRATION 

In the usual recognition problem a series of extraction and classification steps will give rise to a sequence of subpatterns. Making 

the sequence of subpatterns "add up to" an answer to the original 

problem is the job of the integration function in the recognition 

procedure. Integration must therefore control the sequencing of the 

extraction and classification, and handle any feedback that is involved in the recognition. 

Consider the handwriting example, and suppose that the initial 

segment has been classified as belonging to the subpattern of "tailed" 

capital letters, i. e., is one of J, Y, Z. This produces, out of the list 

of 250 first names, a list of perhaps 20 possibilities for the remainder 

of the first name: ames, ohn, oan, vonne, ves, achary, elda, and so on. 

Clearly the use of such a small and specific list of possibilities can 

bring into consideratioh a new group of practical possibilities for the 

extraction and classification of the second segment. As a consequence of this type of feedback, every iteration should be able to restrict itself to a small number of subpatterns. 

If the extraction of segments and their classification proceed independently rather than iteratively, and if there is no effort to correct 

errors in these stages either by context or by error detection and 

iteration, then integration is a relatively trivial step. For problems 

of any complexity, where errors in the earlier aspects cannot be allowed to cause the procedure to fail, integration is a major aspect of 

the procedure. 

If integration is to control iterative processes and use earlier results to make decisions about later ones, then error detection and 

correction become possible. For example, the set of letters J-o-h-u 

is readily recognized as "John". Whether J-o-h-f should be treated 

as a name not on the list depends on probability distributions of that 

outcome under the two subpatterns "John" and "not listed", as well 

as on the consequences of the two possible way of making an erroneous decision. 

CONCLUSION 

We have described a model of pattern recognition, based on treating the problem as related to communication theory. This model 

leads to a structure for recognition procedures in general, and provides a basis for evaluating the thoroughness with which a proposed 

procedure attacks the various aspects of the recognition task. 

Although the discussion may have appeard to stress the difficulties 

of such functions as extraction and classification, our purpose has 

been primarily to warn against a tendency to gloss over or wish 

UNCLASSIFIED 22 
REF ID:A62856 

W.W. JACOBS UNCLASSIFIED 

away certain aspects of the job. We feel that these difficulties are 

surmountable, once they are squarely faced. 

In fact, when the problems are formulated concretely enough, even 

such currently unmanageable tasks as identifying handwritten material by machine can begin to look quite feasible. The use of iterative procedures, which at all points deal with a relatively small set 

of subpatterns, and apply these to narrow the problem successively, 

seems to represent the most hopeful direction for continued exploration. 

APPENDIX 

It appears useful to restate in mathematical language the model 

that has been presented in the preceding pages. This model involves 

M = the space of messages m. 

S = the space of signals s. 

R = the space of records r. 

Associated with each point of M is a conditional probability measure on S: 

Pr[sJm] 

and with each point of Sa conditional probability measure on R: 

Pr[rJs]. 

These induce a conditional probability measure 

Pr[rJm] = J 

8 

Pr[rJs]d Pr[sim]. 

A pattern Pis a partition of M: that is, a set P; of non-overlapping 

classes of messages which together exhaust M. 

P; P; = 0. 

A decision procedure D for recognition is a corresponding partition 

of R: that is a set Di such that 

In order that the validity of a decision procedure can have any 

meaning, the probability measures 

Pr[rl P;] 

23 UNCLASSIFIED 
REF ID:A62856 

UNCLASSIFIED PATTERN RECOGNITION 

must exist. This requires that there be a set of relative probability 

measures over each of the subspaces P;; if these measures are denoted by μ;, then 

Pr[r\P;] =JP; Pr[r\m]dμ.;(m). 

However, the partition P is specified by the recognizer, and therefore the relative measures must exist for any partition P. This can 

happen only if there is a measure μ defined on M, with 

μ;(m) = μ(m) + μ(P;) whenever μ(P,-) > o. 

The problem now reduces to the typical estimation problem of decision theory, with the classes P; corresponding to the states of nature or hypotheses, the sets D; the actions or estimates, and the 

μ(P;) the prior probabilities. 

UNCLASSIFIED 24 
1 

I 

REF ID:A62856 

cor~FIBEtHIAL 

Introduction to Cryptology-IV 

BY WILLIAM F. FRIEDMAN 

Confidential 

Cryptology in the Civil War 

A detailed account of the codes and ciphers of the Civil War in the 

United States of America can hardly be told without beginning with 

a bit of biography about the man who became the first signal officer 

in history and the first Chief Signal Officer of the United States Army, 

Albert J. Myer, the man in whose memory that lovely little U. S. 

Army post adjacent to Arlington Cemetery was named. Myer was 

born on 20 September 1827, and after an apprenticeship in the then 

quite new science of electric telegraphy he entered Hobart College, 

Geneva, New York, from which he was graduated in 1847. From 

early youth he had exhibited a predilection for artistic and scientific 

studies, and upon leaving Hobart he entered Buffalo Medical College, 

receiving the M.D. degree four years later. His graduation thesis, 

"A Sign Language for Deaf Mutes,'' contained the germ of the idea 

he was to develop several years later, when, in 1854, he was commissioned a 1st Lieutenant in the Regular Army, made an Assistant 

25 eot~FIBEr~TIAL 
REF ID:A62856 

eo~~Fl0EtHIAL HISTORY OF CRYPTOLOGY 

Surgeon, and ordered to New Mexico for duty. He had plenty of 

time at this far-away outpost to think about developing an efficient 

system of military "aerial telegraphy," which was what visual signaling was then called. I emphasize the word "system" because, 

strange to say, although instances of the use of lights and other visual 

signals can be found throughout the history of warfare, and their use 

between ships at sea had been practiced by marinets for centuries, 

yet down to the middle of the 19th Century surprisingly little progress had been made in developing methods and instruments for the 

systematic exchange of military information and instructions by means 

of signals of any kind. Morse's practical system of electric telegraphy, developed in the years 1832-35, served to focus attention 

within the military upon systems and methods of inter-communication by means of both visual and electrical signals. In the years 

immediately preceding the Civil War, the U. S. Army took steps to 

introduce and to develop a system of visual signaling for general use 

in the field. It was Assistant Surgeon Myer who furnished the 

initiative in this matter. 

In 1856, two years after he was commissioned assistant surgeon, 

Myer drafted a memorandum on a new system of visual signaling 

and obtained a patent on it. Two years later, a board was appointed 

by the War Department to study Myer's system. It is interesting to 

note that one of the officers who served as an assistant to Myer in 

demonstrating his system before the board was a Lieutenant E. P. 

Alexander, Corps of Engineers. We shall hear more about him 

presently, but at the moment I will say that on the outbreak of war, 

Alexander organized the Confederate Signal Corps. After some successful demonstrations by Myer and his assistants, the War Department fostered a bill in Congress, which gave its approval to his ideas. 

But what is more to the point, Congress appropriated an initial 

amount of $2,000 to enable the Army and the War Department to 

develop the system. The money, as stated in the Act was to be used 

"for manufacture or purchase of apparatus and equipment for field 

signaling." The act also contained another important provision: it 

authorized the appointment, on the Army staff, of one Signal Officer 

with the rank, pay, and allowances of a major of cavalry. On 2 July 

1860, "Assistant Surgeon Albert J. Myer (was appointed) to be Signal 

Officer, with the rank of Major, 27 June 1860, to fill an original 

vacancy," and two weeks later Major Myer was ordered to report to 

the Commanding General of the Department of New Mexico for 

signaling duty. The War Department also directed that two officers 

be detailed as his assistants. During a several months' campaign 

against hostile Navajos, an extensive test of Myer's new system, 

using both flags and torches, was conducted with much success. In 

CO~ffl0Et~TIAL 26 
REF ID:A62856 

W. F. FRIEDMAN co~mDHHIAL 

October 1860, a Lieutenant J. E. B. Stuart, later to become famous 

as a Confederate cavalry leader, tendered his services to aid in signal 

instruction. 

Less than a year after Major Myer was appointed as the first and, 

at that time, the only Signal Officer of the U.S. Army, Fort Sumter 

was attacked and, after a 36-hour bombardment, surrendered. The 

bloody four-year war between the North and the South began. The 

date was 14 April 1861. Myer's system of aerial telegraphy was soon 

to undergo its real baptism under fire, rather than by fire. But with 

the outbreak of war, another new system of military signal communication, signaling by the electric telegraph, began to undergo its first 

thorough test in combat operations. This in itself is very important 

in the history of cryptology. But far more significant in that history 

is a fact that I mentioned at the close of the last lecture, viz, that for 

the first time in the conduct of organized warfare, rapid and secret 

military communications on a large scale became practicable, because 

cryptology and electric telegraphy were now to be joined in a lasting 

wedlock. For when the war began, the electric telegraph had been 

in use for less than a quarter of a century. Although the first use of 

electric telegraphy in military operations was in the Crimean War in 

Europe (1854-56), its employment was restricted to communications 

exchanged among headquarters of the Allies, and some observers 

were very doubtful about its utility even for this limited usage. It 

may also be noted that in the annals of that war there is no record of 

the employment of electric telegraphy together with means for protecting the messages against their interception and solution by the 

enemy. 

On the Union side in the Civil War, military signal operations 

began with Major Myer's arrival in Washington on 3 June 1861. 

His basic equipment consisted of kits containing a white flag with a 

red square in the center for use against a dark background; a red flag 

with a white square for use against a light background; and torches 

for night use. It is interesting to note that these are the elements 

which make up the familiar insignia of our Army Signal Corps. The 

most pressing need which faced Major Myer was to get officers and 

men detailed to him wherever signals might be required, and to train 

them in what had come to be called the "wigwag system," 1 the 

motions of which are depicted in Fig. 1. This training included 

learning something about codes and ciphers, and gaining experience 

in their usages. 

But there was still no such separate entity as a Signal Corps of the 

1 And, of course, the G. I.'s of those days had a pet name for the users of the 

system. They called them "flag floppers." 

27 co~mDEt~TIAL 
REF ID:A62856 

cotmDHHIAL HISTORY OF CRYPTOLOGY 

1--·:/· 

First "Motion - "One" - "1" 

/··· 

·~·······<:\ 

Second Motion -''I'wci"'2" "One Two"- "12" 

· .. ~··. 

···-.. 

"Two - One -Two - One" - "2121" "Three"-"3" or"Front" 

Fig. 1. 

cotmDDHIAL 28 
REF ID:A62856 

w. F. FRIEDMAN EOt~FIBEt~TIAL 

Army. Officers and enlisted men were merely detailed for service 

with Major Myer for signaling duty. It was not until two years 

after the war started that the Signal Corps was officially established 

and organized as a separate branch of the Army, by appropriate 

Congressional action. 

In the meantime, another signaling organization was coming into 

being-an organization which was an outgro\\'.th of the government's 

taking over control of the commercial telegraph companies in the 

United States on 25 February 1862. There were then only three in 

number: the American, the Western Union, and the Southwestern. 

The telegraph lines generally followed the right-of-way of the railroads. The then Secretary of War, Simon Cameron, sought the aid 

of Thomas A. Scott, of the Pennsylvania Railroad, who brought some 

of his men to Washington for railroad and telegraphic duties with the 

Federal Government. From a nucleus of four young telegraph operators grew a rather large military telegraph organization which was 

not given formal status until on 28 October 1861 President Lincoln 

gave Secretary Cameron authority to set up a "U.S. Military Telegraph Department" under a man named Anson Stager, who, as general superintendent of the Western Union, was called to Washington, 

commissioned a captain (later a colonel) in the Quartermaster Corps, 

and made superintendent of the Military Telegraph Department. 

Only about a dozen of the members of the Department became commissioned officers, and they were made officers so that they could 

receive and disburse funds and property; all the rest were civilians. 

The U.S. Military Telegraph "Corps," as it soon came to be designated, without warrant, was technically under Quartermaster General 

Meigs, but for all practical purposes it was under the immediate and 

direct control of the Secretary of War, a situation admittedly acceptable to Meigs. There were now two organizations for signaling in the 

Army, and it was hardly to be expected that no difficulties would 

ensue from the duality. In fact, the difficulties began very soon, as 

can be noted in the following extract from a lecture before the 

Washington Civil War Round Table, early in 1954, by Dr. George 

R. Thompson, Chief of the Historical Division of the Office of the 

Chief Signal Officer of the U.S. Army: 

The first need for military signals arose at the important Federal 

fortress in the lower Chesapeake Bay at Fort Monroe. Early in June, 

Myer arrived there, obtained a detail of officers and men and began 

schooling them. Soon his pupils were wig-wagging messages from a 

small boat, directing fire of Union batteries located on an islet in 

Hampton Roads against Confederate fortifications near Norfolk. 

Very soon, too, Myer began encountering trouble with commercial wire 

telegraphers in the area. General Ben Butler, commanding the Federal Department in southeast Virginia, ordered that wire telegraph 

29 eo~~FIBEt~TIAL 
REF ID:A62856 

eo~~FIBEtHIAL HISTORY OF CRYPTOLOGY 

facilities and their civilian workers be placed under the signal officer. 

The civilians, proud and jealous of their skills in electrical magic, 

objected in no uncertain terms and shortly an order arrived from the 

Secretary of War himself who countermanded Butler's instructions. 

The Army signal officer was to keep hands off the civilian telegraph 

even when it served the Army. 

I have purposely selected this extract from Dr. Thompson's presentation because in it we can clearly hear the first rumblings of that 

lengthy and acrimonious feud between two signaling organizations 

whose uncoordinated operations and rivalry greatly reduced the 

efficiency of all signaling operations of the Federal Army. As already 

indicated, one of these organizations was the U.S. Military Telegraph 

"Corps," hereinafter abbreviated as the USMTC, a civilian organization which operated the existing commercial telegraph systems for 

the War Department, under the direct supervision of the Secretary 

of War, Edwin M. Stanton. The other organization was, of course, 

the infant Signal Corps of the United States Army, which was not 

yet even established as a separate Branch, whereas the USMTC had 

been established in October 1861, as noted above. Indeed, the 

Signal Corps had to wait until March 1863, two years after the outbreak of war, before being established officially. In this connection it 

should be noted that the Confederate Signal Corps had been established a full year earlier, in April 1862. Until then, as I've said 

before, for signaling duty on both sides, there were only officers who 

were individually and specifically detailed for such duty from other 

branches of the respective Armies of the North and the South. 

Trouble between the USMTC and the Signal Corps of the Union 

Army began when the Signal Corps became interested in signaling 

by electric telegraphy and began to acquire facilities therefor. 

As early as in June 1861, Chief Signal Officer Myer had initiated 

action toward acquiring or obtaining electrical telegraph facilities for 

use in the field but with one exception nothing happened. The exception was in the case of the episode in the military department in 

southeast Virginia, commanded by General Benjamin Butler, an 

episode that clearly foreshadowed the future road for the Signal Corps 

in regard to electrical signaling: the road was to be closed and barred. 

In August 1861, Colonel Myer tried again and in November of the 

same year he recommended in his annual report that $30,000 be 

appropriated to establish an electric signaling branch in the Signal 

Corps. The proposal failed to meet the approval of the Secretary of 

War. One telegraph train, however, which had been ordered by 

Myer many months before, was delivered in January 1862. The 

train was tried out in an experimental fashion, and under considerable 

difficulties, the most disheartening of which was the active opposition 

of persons in Washington, particularly the Secretary of War. So, for 

co~~f\OOH\AL 30 
REF ID:A62856 

W. F. FRIEDMAN COt~FIE>EtHIAL 

practically the whole of the first two years of the war, signal officers 

on the Northern side had neither electrical telegraph facilities nor 

Morse operators-they had to rely entirely on the wig-wag system. 

However, by the middle of 1863 there were thirty "flying-telegraph" 

trains in use in the Federal Army. Here's a picture of such a train. 

The normal length of field telegraph lines was five to eight miles, 

though in some cases the instruments had worked at distances as 

great as twenty miles. But even before th~ Signal Corps began to 

A drawing from Myer's Mdnual o1 Signa/1 illustrating the 6eld, or l!ying, telegraph. It 1hows 

the wagon witb batteries and instruments. The wire (in this case presumably bare copper, 

since it is being strung on insulators on poles) is being run out from a reel carried by two men. 

Tbe linesmen are using a crowbar to open holes to receive the lance poles. Myer estimated that 

2Yz. miles of such wire line could be put up in U1 hour. 

Fig. 2. 

acquire these facilities, there had been agitation to have them, as well 

as their Signal Corps operating personnel, all turned over to the 

USMTC, which had grown into a tightly-knit organization of over 

1,000 men and had become very influential in Washington, especially 

by virtue of its support from Secretary of War Stanton. As a consequence, the USMTC had its way. In the fall of 1863, it took over 

all the electric telegraph facilities and telegraph operators of the 

Signal Corps. Colonel Myer sadly wrote: "With the loss of its 

electric lines the Signal Corps was crippled." 

So now there were two competing signal organizations on the 

Northern side: The U.S. Army's Signal Corps, which was composed 

entirely of military personnel with no electric telegraph facilities (but 

was equipped with means for visual signaling), and the USMTC, 

which was not a part of the Army, being staffed almost entirely with 

civilians, and which had electric telegraph facilities and skilled Morse 

31 
REF ID:A62856 

COt~FIBEt~flAL HISTORY OF CRYPTOLOGY 

operators (but no means or responsibilities for visual signaling or 

"aerial telegraphy" which, of course, was old stuff). "Electric telegraphy" was now the thing. The USMTC had no desire to share 

electric telegraphy with the Signal Corps, a determination in which 

it was most ably assisted by Secretary of War Stanton, for reasons 

that fall outside the scope of the present lecture. 

However, from a technical point of view it is worth going into this 

rivalry just a bit, if only to note that the 'personnel of both organizations, the military and the civilian, were not merely signalmen and 

telegraph operators: they served also as cryptographers and were 

therefore entrusted with the necessary cipher books and cipher keys. 

Because of this, they naturally became privy to the important secrets 

conveyed in cryptographic communications and they therefore 

enjoyed status as VIP's. This was particularly true of members of 

the USMTC, because they, and only they, were authorized to be 

custodians and users of the cipher books. Not even the commanders 

of the units they served had access to them. For instance, on the 

one and only occasion when General Grant forced his cipher operator, 

a civilian named Beckwith, to turn over the current cipher book to a 

colonel on Grant's staff, Beckwith was immediately discharged by the 

Secretary of War and Grant was reprimanded. A few days later, 

Grant apologized and Beckwith was restored to his position. But 

Grant never again demanded the cipher book held by his telegraph 

operator. 

The Grant-Beckwith affair alone is sufficient to indicate the lengths 

to which Secretary of War Stanton went to retain control over the 

USMTC, including its cipher operators, and its cipher books. In 

fact, so strong a position did he take that on 10 November 1863, 

following a disagreement over who should operate and control all the 

military telegraph lines, Myer, by then full Colonel, and bearing the 

imposing title "Chief Signal Officer of the United States Army," a 

title he had enjoyed for only two months, was peremptorily relieved 

from that position and put on the shelf. Not long afterward, and 

for a similar reason, Myer's successor, Lieutenant Colonel Nicodemus, 

was likewise summarily relieved as Chief Signal Officer by Secretary 

Stanton; indeed, he was not only removed from that position-he was 

"dismissed the Service." Stanton gave "phoney" reasons for 

dismissing Colonel Nicodemus, but I am glad to say that the latter 

was restored his commission in March 1865, by direction of the 

President; also by direction of the President, Colonel Myer was 

restored to his position as Chief Signal Officer of the U.S. Army on 

25 February 1867. 

When Colonel Myer was relieved from duty as Chief Signal Officer 

in November 1863, he was ordered to Cairo, Illinois, to await orders 

co~mBEtHIAL 32 
REF ID:A62856 

W. F. FRIEDMAN co~mDEtHIAL 

for a new assignment. Very soon thereafter he was either designated 

(or he may have himself decided) to prepare a field manual on signaling and there soon appeared, with a prefatory note dated January 

1864, a pamphlet of 148 pages, a copy of which is now in the Rare 

Book Room of the Library of Congress. The title page reads as 

follows: 

"A Manual of Signals: for the use of signal officers in the field. By 

Col. Albert J. Myer, Signal Officer of the Anny, Washington, D. C., 

1864." 

Even in this first edition, printed on an Army press, Myer devoted 

nine pages to a reprint of an article from Harper's Weekly entitled 

"Curiosities of Cipher," and in the second edition, 1866, he expanded 

the section on cryptography to sixty pages. More editions followed 

and I think we may well say that Myer's Manual, in it several editions, 

was the pioneer American text on military signaling. But I'm sorry 

to say that as regards cryptology it was rather a poor thing. Poe had 

done better twenty years before that in his essay entitled "A few 

words on secret writing." 

Because of its historic nature, you may like to see what Myer's 

original "wig-wag code" was like. It was called "a two-element 

code" because it employed only two digits, 1 and 2, in permutations 

of 1, 2, 3 and 4 groups. For example, A was represented by the permutation 22; B, by 2122; and C, by 121, etc. In flag signaling, a 

"l" was indicated by a motion to the left, and a "2" by a motion to 

the right. Later these motions were reversed, for reasons which 

must have been good but are now not obvious.* Here is Myer's twoelement code which continued to be used until 1912: 

GENERAL SERVICE CODE 

A - 22 M - 1221 y - 111 

B - 2122 N - 11 z - 2222 

c 121 0 21 & - 1111 

D - 222 p - 1212 ing - 2212 

E - 12 Q - 1211 tion - 1112 

F - 2221 R - 211 

G - 2211 s - 212 End of word -3 

H - 122 T - 2 End of sentence - 33 

I 1 u - 112 End of message - 333 

J - 1122 v - 1222 Affirmative - 22.22.22.3 

K - 2121 w - 1121 Repeat - 121.121.121 

L - 221 x - 2122 Error - 212121 

Note: No. 3 (end of word) was made by a forward downward motion, 

called "front". There were about a dozen more signals, for numerals, for frequently used short sentences, etc. 

*This reversal can be seen in Fig. 1. 

33 COt-lFIDEtHIAL 
I 

·I 

I 

REF ID:A62856 

co~meet~flAt HISTORY OF CRYPTOLOGY 

We must turn our attention now to the situation as regards the 

organization for signaling in the Confederate Army. It is of considerable interest to note that in the first great engagement of the 

War, that of the first Bull Run battle, the Confederate Signal Officer 

was that young Lieutenant, E. P. Alexander, who had assisted in 

demonstrating the wig-wag system before a board appointed by the 

War Department to study Myer's system. Alexander, now a Captain 

in grey, used Myer's system during the battle, which ended in disaster 

for the Union forces; and it is said that Alexander's contribution by 

effective signaling was an important factor in the Confederate victory. 

Dr. Thompson, whom I have quoted before, says of this battle: 

Thus the fortunes of war in this battle saw Myer's system of signals 

succeed, ironically, on the side hostile to Myer. Because of general 

unpreparedness and also some disinterest and ignorance, the North 

had neither wig-wag signals nor balloon observations. 

The only communication system which succeeded in signal work for 

the Union Army was the infant USMTC. But the Confederate 

system under Alexander, off to a good start at Bull Run, throughout 

the war operated with both visual and electric telegraphy, and the 

Confederates thought highly enough of their signal service to establish 

it on an official basis, on 19 April 1862, less than a year after that 

battle. Thus, although the Confederate Signal Corps never became 

a distinct and independent branch of the Army as did the Union 

Signal Corps, it received much earlier recognition from the Confederate Government than did the Signal Corps of the Federal Government. Again quoting Dr. Thompson: 

The Confederate Signal Corps was thus established nearly a year 

earlier than its Federal counterpart. It was nearly as large, numbering some 1,500, most of the number, however, serving on detail. The 

Confederate Signal Corps used Myer's system of flags and torches. 

The men were trained in wire telegraph, too, and impressed wire facilities as needed. But there was nothing in Richmond or in the field 

comparable to the extensive and tightly controlled civilian military 

telegraph organization which Secretary Stanton ruled with an iron hand 

from Washington. 

We come now to the codes and ciphers used by both sides in the 

war, and in doing so we must take into consideration the fact that on 

the Union side, there were, as I have indicated, two separate organizations for signal communications; one for visual signaling, the other 

for electric. We should therefore not be too astonished to find that 

the cryptosystems used by the two competing organizations were 

different. On the other hand, on the Confederate side, as just noted, 

there was only one organization for signal communications, the Signal 

Corps of the Confederate States Army, which used both visual and 

electric telegraphy, the latter facilities being taken over and employed 

co~monn1><L 34 
REF ID :A62856 ~!11',I 

w. F. FRIEDMAN co~•FIE>HHIAL 

when and where they were available. There were reasons for this 

marked difference between the way in which the Union and the Confederate signal operations were organized and administered but I do 

not wish to go into them now. One reason, strange to say, had to do 

with the difference between the cryptocommunication arrangements 

in the Union and in the Confederate Armies. 

We will discuss the cryptosystems used by the Federal Signal Corps 

first and then those of the Confederate Signal Corps. Since both 

corps used visual signals as their primary means, we find them employing Myer's visual-signaling code shown above. At first both 

sides sent unenciphered messages; but soon after learning that their 

signals were being intercepted and were being read by the enemy, 

each side decided to do something to protect its messages. Initially 

both decided on the same artifice, viz, changing the visual-signaling 

equivalents for the letters of the alphabet, so that, for instance, "22" 

was not always "A," etc. This sort of changing-about of values soon 

became impractical, since it prevented memorizing the wig-wag equivalents once and for all. The difficulty in the Union Army's Signal 

Corps was solved by the introduction into usage of a cipher disk 

invented by Myer himself. A full description of the disk in its 

various embodiments will be found in Myer's Manual, but here's a 

picture of three forms of it. You can see how readily the visual wigwag equivalents for letters, figures, etc., can be changed according to 

some pre-arranged indicator for juxtaposing concentric disks. In my 

Fig. 3 the top left disks (Fig. 1 of Myer's Plate XXVI) show that the 

letter A is represented by 112, B, by 22, etc. By moving the two 

circles to a different juxtaposition a new set of equivalents will be 

established. Of course, if the setting is kept fixed for a whole message 

the encipherment is strictly monoalphabetic; but Myer recommends 

changing the setting in the middle of the message or, more specifically, 

at the end of each word, thus producing a sort of polyalphabetic cipher 

which would delay solution a bit. An alternative way, Myer states, 

would be to use what he called a "countersign word," but which we 

call a keyword, each letter of which would determine the setting of the 

disk for a single word or for two consecutive words, etc. Myer apparently did not realize that retaining or showing externally, that is, 

in the cipher text, the lengths of the words of the plain text very 

seriously impairs the security of the cipher message. A bit later we 

shall discuss the security afforded by the Myer disk in actual practice. 

In the Confederate Signal Corps, the system used for encipherment 

of visual signals was apparently the same as that used for enciphering 

telegraphic messages, and we shall soon see what it was. Although 

Myer's cipher disk was captured a number of times, it was apparently 

disdained by the Confederates, who preferred to use a wholly different 

35 co~•FIE>E~HIAL 
REF ID:A62856 

COt~FIDnHIAL HISTORY OF CRYPTOLOGY 

Figure 1. 

Two Discs. 

ii!lil111 

Vertical Section 

figure 3. 

g 

Figure 4. 

Plan for Service Discs 

F'igul'e fi. 

Figure 2. 

Two Discs. 

!1110111! 

"'P"'F .. - - ~.-~.~--~--.:·.--:-:-. --~ -=H .... £__ - H - -- ~>=:~:.......-~ ~-- - --r=::...-::TVertical Section eXhibiting plan fbr four Discs. 

Fig. 3. 

CONF19E~Hll'<L 36 
REF ID:A62856 

W. F. FRIEDMAN COt-~F19HHIAL 

type of device, as will be described presently, for both visual and 

electric telegraphy. 

So much for the cryptosystems used in connection with visual 

signals by the Signal Corps of both the North and the South, systems 

which we may designate as "tactical ciphers." We come now to the 

systems used for what we may call "strategic ciphers," because the 

latter were usually exchanged between the seat of Government and 

field commanders, or among the latter. In, the case of these communications the cryptosystems employed by each side were quite 

different. 

On the Northern side the USMTC used a system based upon what 

we now call transposition but in contemporary accounts they were 

called "route ciphers" and that name has stuck. The designation 

isn't too bad, because the processes of encipherment and decipherment, though dealing not with the individual letters of the message 

but with entire words, involves following the prescribed paths or 

routes in a diagram in which the message is written. I know no 

simpler or more succinct description of the route cipher than that 

given by one of the USMTC operators, J. E. O'Brien, in an article in 

Century Magazine, XXXVIII, September 1889, entitled "Telegraphing 

in Battle": 

The principle of the cipher consisted in writing a message with an 

equal number of words in each line, then copying the words up and 

down the columns by various routes, throwing in an extra word at the 

end of each column, and substituting other words for important names 

and verbs. 

A more detailed description in modern technical terms would be as 

follows: A system in which in encipherment the words of the plaintext message are inscribed within a matrix of a specified number of 

rows and columns, inscribing the words within the matrix from left to 

right, in successive lines and rows downward as in ordinary writing, 

and taking the words out of the matrix, that is, transcribing them, 

according to a prearranged route to form the cipher message. The 

specific routes to be followed were set forth in numbered booklets, 

each being labeled "War Department Cipher" followed by a number. 

In referring to them hereinafter I shall use the term "cipher books," 

or sometimes, more simply, the term "ciphers," although the cryptosystem involves both cipher and code processes. It is true that the 

basic principle of the system, that of transposition, makes the system 

technically a cipher system as defined in our modern terminology; 

but the use of "arbitraries," as they were called, that is, words arbitrarily assigned to represent the names of persons, geographic points, 

important nouns and verbs, etc., makes the system technically a code 

system as defined in our modern terminology. 

37 COt'4flf)Et'4"flAL 
REF ID:A62856 

co~~FIDHHIAL HISTORY OF CRYPTOLOGY 

There were in all about a dozen cipher books used by the USMTC 

throughout the war. For the most part they were employed consecutively, but, it seems that sometimes two different ones were 

employed concurrently. They contained not only the specific routes 

to be used but also indicators for the routes and for the sizes of the 

matrices; and, of course, there were lists of code words, with their 

meanings. These route ciphers were supposed to have been the 

invention of Anson Stager, whom I have mentioned before in connection with the establishment of the USMTC, and who is said to have 

first devised such ciphers for General McClellan's use in West Virginia, 

in the summer of 1861, before McClellan came to Washington to 

assume command of the Army of the Potomac. 

Anson Stager and many others thought that he was the original 

inventor of the system, but such a belief was quite in error because 

word-transposition methods similar to Stager's were in use hundreds 

of years before his time. For instance, in 1685, in an unsuccessful 

attempt to invade Scotland, in a conspiracy to set the Duke of 

Monmouth on the throne, Archibald Campbell, 9th Earl of Argyll, 

suffered an unfortunate "accident". He was taken prisoner and 

beheaded by order of James the Second. The communications of the 

poor Earl were not secure, and when they fell into government hands 

they were soon deciphered. The method Argyll used was that of 

word transposition, and if you are interested in reading a contemporary account of how it was solved, look on pages 56-59 of that little 

book I mentioned before as being one of the very first books in English 

dealing with the subject of cryptology, that by James Falconer, 

entitled Cryptomenysis Patefacta: Or the Art of Secret Information 

Disclosed Without a Key, published in London in 1685. There you 

will find the progenitor of the route ciphers employed by the USMTC, 

180 years after Argyll's abortive rebellion. 

The route ciphers employed by the USMTC are fully described in 

a book entitled The Military Telegraph during the Civil War, by 

Colonel William R. Plum, published in Chicago in 1882. I think 

Plum's description of them is of considerable interest and I recommend his book to those of you who may wish to learn more about 

them, but they are pretty much all alike. If I show you one example 

of an actual message and explain its encipherment and decipherment 

I will have covered practically the entire gamut of the route ciphers 

used by the USMTC, so basically very simple and uniform were they. 

And yet, believe it or not, legend has it that the Southern signalmen 

were unable to solve any of the messages transmitted by the USMTC. 

This long-held legend I find hard to believe. In all the descriptions 

I have· encountered in the literature not one of them, save the one 

quoted above from O'Brien, tries to make these ciphers as simple as 

eot~FIBDUIAL 38 
REF ID:A62856 

W. F. FRIEDMAN co~~FIDHHIAL 

they really were; somehow, it seems to me, a subconcsious realization 

on the part of Northern writers, usually ex-USMTC operators, of the 

system's simplicity prevented a presentation which would clearly 

show how utterly devoid it was of the degree of sophistication one 

would be warranted in expecting in the secret communications of a 

great modem army in the decade 1860-1870, three hundred years 

after the birth of modern cryptography in the papal states of Italy. 

Let us take the plain text of a message which Plum (p. 58) used in 

an example of the procedure in encipherment. The cipher book 

involved is No. 4 and I happen to have a copy of it so we can easily 

check Plum's work. Here's the message to be enciphered: 

For Simon Cameron 

Washington, D. C. 

July 15, 1863 

I would give much to be relieved of the impression that Meade, 

Couch, Smith and all, since the battle of Gettysburg, have striven only 

to get the enemy over the river without another fight. Please tell me 

if you know who was the one corps commander who was for fighting, in 

the council of war on Sunday night. 

(Signed) A. Lincoln 

Plum shows the word-for-word encipherment in a matrix of seven 

columns and eleven rows. 2 He fails to tell us why a matrix of those 

dimensions was selected; presumably the selection was made at 

random, which was certainly permissible. (See fig. 4.) 

Note the seven "nulls" (non-significant, or "blind" words) at the 

tops and bottoms of certain columns, these being added to the cipher 

text in order to confuse a would-be decipherer. At least that was the 

theory, but how effective this subterfuge was can be surmised, once 

it became known that employing nulls was the usual practice. Note 

also the two nulls (bless and him) at the end of the last line to complete that line of the matrix. Words in italics are "arbitraries" or 

code words. 

The cipher message is then copied down following the route prescribed by the indicator "BLONDE," as given on page 7 of Cipher 

Book No. 4 for a message of 11 lines. The indicator could have also 

been "LINIMENT." 

2 Ruled paper was provided to aid in accuracy. In the diagram the upper 

of each pair of lines of writing is the cipher, the lower one, the plain text. 

Simon Cameron was Lincoln's Secretary of War until Jan 1862, when he was 

replaced by Edwin M. Stanton. If this message cited by Plum is authentic, 

and there is no reason to doubt this, then Cameron was still in friendly contact with Lincoln, possibly as a special observer. 

39 CO!lJFIQE!ltTIAL 
REF ID:A62856 

eot~FIBEtHIAL HISTORY OF CRYPTOLOGY 

1 2 3 4 5 6 7 

(heavy) (county) (square) 

(null) (null) (null) 

Incubus Stewart Brown Norris Knox Madison 

Wash., D.C. July 15th 18 60 3 for 

sigh man Cammer on flea I wood 

Simon Cameron (period) I would 

give much Toby trammeled serenade impression that 

give much to be relieved of the impression that 

Bunyan bear ax cat children and awl 

Meade , (comma) Couch , (comma) Smith and all 

bat since the knit of get ties 

, (comma) since the battle of Gettys 

large ass have striven only to get 

burg , (comma) have striven only to get 

village skeleton turnip without another optic hound 

the enemy over the river without another fight (period) 

Please tell me if you no who 

Please tell me if you know whQ 

was the Harry Madrid locust who was 

was the one corps commander who was 

for 

for 

on 

on 

oppressing bitch quail counsel 

fighting ,(comma) in the council 

Tyler Rustle upright Adrian 

Sunday night Signature A. Lincoln 

(monkey) (silk) (martyr) 

(null) (null) (null) 

Fig. 4. 

s 1 ,f ..t 

f' Vt 1-f I.I 

II // f 

t 1- I 

Wroom ... ..... !.. ......................... ~1.-,. 

Wll&elld ........... . . ... 4.. ........ ·-····· ............. 1-po 

!1 ............. ········""'"'" ::+ ······'-' ............ 

Beptnd ....• 

.r ··················"'··· :~·.: ............................................ :::~.:: ......................................... .. :1-n 

:::::..:: ::: ::::: : :::::::::::.:::i:::::::::··:::::::::::.·.::.:::::::::::·~;~: 

::'.~::··············· : ::::::::::: ::h:::: :::.~:::::~.::::: .~::::::::::::::::::::;: m.............. . ..... //... .........................................• Llmm ... 

Fig. s. 

CONFIBENTIAL 40 

of war 

of war 

bless him 

(null) (null) 

(suicide) 

(null) 
REF ID:A62856 

W. F. FRIEDMAN eo~~FIDnHIAL 

To explain the diagram at the top of Fig. 5 I will show you the 

"Directions for Use" which appear on the reverse side of the title page 

of "War Department Cipher No. 4," because I'm afraid you wouldn't 

believe me if I merely told you what they say. In Fig. 6 is a picture 

of the title page and I follow it with Fig. 7, a photograph of what's on 

its reverse. 

WAR DEPARTMENT CIPHER NO. 4. 

Fig. 6. 

DIRECTIONS FOR USE. 

Tu find the rouh•, rC'H!I th1• fijlUM• in tl1t t.11\•k ut top of Jlll)ott' from J .. ft 

to rip;ht in thf' or<ln that tl1t'~· •Wl'llr alt1>rnutdy in tlu· upper urnl lower 

linell, the two illt<'mwclintt• Jilw,. of fij!ure~ ha\'injl 110 1·0111wrtiun with 

th1• rouk, b<'inl( iutro•lw·i·d >'i111ply !I>' n hlind, the uppn lhw of tiμ-nl'el< 

d!'noting th1· rnut(• ,/,.,(',. tlw c·olnnm unrl tho· low1'r linr· ''I'· 

Jo;XAMf'l.K 

S1•1• Jllllotl' 14 ; 7 l'O!Umll>', 

R1mt('-lTp tlu• &1; down th" fith; up tlw J:-;t; (lnwH tlw 7th; up tlw 

2d; dnwll tht> 4th; up the 5th. 

Conu1wnc1• a cipher with orn· of th1· '· Ji]l(· indicatort-,'' tnken from 

tmm{' paj!P ns routt· rn~ed, wlikh wor(I mu .. t irnlicak the numlll•r of li1ws 

rn th<> mc~SHJ.(<'. 17,.r tw" wnr1I~ for m01·1· th11n !wNty linci-;. 

Fig. 7. 

Do you imagine that the chap who was responsible for getting this 

cipher book approved ever thought about what he was doing when he 

caused those "Directions for Use" to be printed? It doesn't seem 

possible. All he would have had to ask himself was, "Why put this 

piece of information in the book itself?" Cipher books before this 

have been captured. Suppose this one falls into enemy hands; can't 

he read, too, and at once learn about the intended deception? Why 

go to all the trouble of including "phoney" routes anyway? If the 

book doesn't fall into enemy hands what good are the "phoney" 

routes anyway? Why not just indicate the routes in a straightforward manner, as had been done before? Thus: "Up the 6th 

column (since "6" is the first number at the left of the diagram), 

down the 3rd, up the 5th, down the 7th, up the 1st, down the 4th and 

down the 2nd." This matter is so incredibly fatuous that it is hard 

to understand how sensible men-and they were sensible-could be 

so illogical in their thinking processes. But there the "Directions 

for Use" stand, for all the world to see and to judge. 

Now for the transposition step. The indicator "BLONDE" signifies a matrix of seven columns and eleven rows, with the route set 

41 COMFIDEtHIAL 
REF ID:A62856 

COl~flf)EtHIAL HISTORY OF CRYPTOLOGY 

forth above, viz, up the 6th column, down the 3rd, etc., so that the 

cipher text with a "phoney" address and signature, 3 becomes as 

follows: 

TO A. HARPER CALDWELL, Washington,.,D. C. 

Cipher Operator, Army of the Potomac: 

Blonde bless of who no optic to get and impression I Madison square 

Brown cammer Toby ax the have turnip me Harry bitch rustle silk 

Adrian counsel locust you another only of children serenade flea Knox 

County for wood that awl ties get hound who was war him suicide on 

for was please village large bat Bunyan give sigh incubus heavy Norris 

on trammeled cat knit striven without if Madrid quail upright martyr 

Stewart man much bear since ass skeleton tell the oppressing Tyler 

monkey. 

(Signed) D. HOMER BATES 

Note that the text begins with the indicator "BLONDE". In 

decipherment the steps are simply reversed. The indicator tells 

what size matrix to outline; the words beginning "bless of who no 

optic ... " are inscribed within the matrix: up the 6th column; then, 

omitting the "check word" or "null" (which in this case is the word 

"square") down the 3rd column, etc. The final result should correspond to what is shown in Fig. 4. There then follows the step of 

interpreting orthographic deviations, such as interpreting "sigh", 

"man," "cammer," and "on" as Simon Cameron; the word "wood" 

for "would", etc. The final step reproduces the original plain text. 

Save for one exception, all the route ciphers used by the USMTC 

conformed to this basic pattern. The things that changed from one 

cipher book to the next were the indicators for the dimensions of the 

matrices and for the routes, and the "arbitraries" or code equivalents 

for the various items comprising the "vocabulary," the number of 

them increasing from one edition to the next, just as might be expected. The sole exception to this basic pattern is to be seen in 

Cipher Book No. 9 and on only one page of the book. I will show 

you that page. (See fig. 8.) 

What we have here is a deviation from the straightforward route 

transposition, "up the ... column, down the ... column," etc. By 

introducing one diagonal path in the route (the 6th, 7th, 8th, 9th, 

10th words in a message of :five columns, and the 1st, 2nd, 3rd, 4th, 

5th, and 6th words in a message of six columns) the simple up and 

down route no longer holds true. The words on the diagonal interrupt the normal up and down paths and introduce complexities in 

3 It was the usual practice to use for address and signature the names of 

the USMTC operators concerned. 

COt~FIDEtHIAL 42 
REF ID:A62856 

W. F. FRIEDMAN EOt~FIBEtHIAL 

12 

Jfessnge or Division of ... 6 ... Lines. 

COMME?iCEMENT WORBS. 

r;:;~~1n} .......... 6: ........ j ~Cl~li.n} ........ Q ....... 1 Nu~l1°k} ........ 7 ......... . Chase cor.UMNR McDoweJl cm.t:MNS Sibley coLUMNR 

Scvt~ RouT•.-Up the •.. .Jf column; down the .... J. .. ; up the .... f)~.; down the ..... 2; 

up the .. .J .... ; down the .... O .. ; up the .... Z. 

1ivt cc]uinm, If 2~ ;:6 16 6 

I l.i Z4 27 7 s 

/j 23 ~ 17 -f 

IZ 'l 2S !ff 3 

10 zz 29 I 'f 2 

II ZI JO 20 I 

" 

x x 

Six colinnns. 6 17 27 J6 2. (; 16 

7 5 Zi' Jf 2i If 

~ I~ 4- 34 Z4 I LI 

"! Jq zq ._1, z; 13 

10 20 30 33 2 { 2. 

II 2f j/ 32 12 I 

Fig. 8. 

the method. In fact, the complexities, seemed to be a bit too much 

for the USMTC cipher operators because, as far as available records 

show, these complicated routes were never used. 

I now wish to make a number of general and a few specific comments 

on Plum's description of the cryptosystems used by the USMTC. 

First, we have learned that although Anson Stager has been credited 

with inventing the type of cipher under consideration in this study, 

he was anticipated in the invention by about 200 years. Also, he is 

given the lion's share of the credit for devising those ciphers although 

he did have a number of collaborators. Plum names four of them, 

presumably because he thought them worthy of being singled out for 

43 eortc1F1e~rtc111At 
co~~FIBHHIAL HISTORY OF CRYPTOLOGY 

particular attention. Plum and others tell us that copies of messages 

handled by the USMTC were sometimes intercepted by the enemy 

but not solved. He cites no authority for this last statement, merely 

saying that such intercepts were published in the newspapers of the 

Confederacy with the hope that somebody would come up with their 

solution. And it may be noted that none of the Confederate accounts 

of war activities cite instances of the solution of intercepted USMTC 

messages, although there are plenty of citations of instances of interception and solution of enciphered visual transmissions of the Federal 

Army's Signal Corps. 

Plum states that 12 different cipher books were employed by the 

Telegraph Corps, but I think there were actually only eleven. The 

first one was not numbered, and this is good evidence that a long 

war was not expected. This first cipher book had 16 printed pages. 

But for some reason, now impossible to fathom, the sequence of numbered books thereafter was as follows: Nos. 6 and 7, which were 

much like the first (unnumbered) one; then came Nos. 12, 9, 10-in 

that strange order; then came Nos. 1 and 2; finally came Nos. 3, 4, 

and 5. (Apparently there was no No. 8, or No. 11-at least they 

are never mentioned.) It would be ridiculous to think that the irregularity in numbering the successive books was for the purpose of 

communication security, but there are other things about the books 

and the cryptosystem that appear equally silly. There may have 

been good reasons for the erratic numbering of the books, but if so, 

what they were is now unknown. Plum states that No. 4, the last 

one used in the war, was placed into effect on 23 March 1865, and 

that it and all other ciphers were discarded on 20 June 1865. However, as noted, there was a No. 5, which Plum says was given a limited distribution. I have a copy of it, but whether it was actually 

put into use I do not know. Like No. 4, it had 40 pages. About 

20 copies were sent to certain members of the USMTC, scattered 

among 12 states; and, of course, Washington must have had at least 

one copy. 

We may assume with a fair amount of certainty that the first (the 

unnumbered) cipher book used by the USMTC was merely an elaboration of the one Stager produced for the communications of the 

governors of Ohio, Indiana and Illinois, and of which a copy is given 

by only one of the writers who have told us about these ciphers, 

namely, David H. Bates. Bates, in his series of articles entitled 

"Lincoln in the Telegraph Office" (The Century Magazine, Vol. 

LXXIV, Nos. 1-5, May-Sept, 1907) 4 shows a facsimile thereof (p. 

' The series was then put out in book form under the same title by the D. 

Appleton-Century Company, New York, 1907, reprinted in 1939. · 

EOt~FIBEtHIAL 44 
REF ID:A62856 

W. F. FRIEDMAN EO~~FIBEtHIAL 

292, June 1907 issue), and I have had as good a reproduction made 

of it as is possible from the rather poor photographic facsimile. The 

foregoing cipher is the prototype upon which all subsequent cipher 

books were based, the first of the War Department series being the 

one shown by Plum. 

l'M:SllllLE or THE TELEGRAPHIC CIPHER-CODE USED BY THE UNITED 

STATES GOVEJlNME."iT IN 1861 

Fig. 9. 

When these ciphers came into use it was not the practice to mis .. 

spell certain words intentionally; but as the members of the USMTC 

(who, as I've told you, not only served as telegraph operators but 

also as cipher clerks) developed expertness, the practice of using nonstandard orthography was frequently employed to make solution of 

messages more difficult. You have already seen examples of this 

practice, and one can find hundreds of other examples of this sort of 

artifice. Then, further to increase security, more and more code 

equivalents were added to represent such things as ordinal and cardinal numbers, months of the year, days of the week, hours of the day, 

punctuation, etc. As a last step, additional code equivalents for 

frequently used words and phrases were introduced. One good example of two typical pages from one of these books will characterize 

them all. 

45 C0~4 FIBEt~TIAL 
COl~FIO~l~llAL 

REF ID:A62856 

HISTORY OF CRYPTOLOGY 

12 

Cairw1M.&U 

'""'" .. . . .A,.GW..w.u.f.,,,,~ .. , .. ... W..11SIMIJNW. .lux"WM> .. . 'i.1'13.'11M1i""1. fu.I( IQ.WM .. 

•w••···· .... -.. S.f..U.fl'.'1 .•. ~ ;;,,,.,"""'I C"1WH.Sn..fu .. !<U('1<k.><h. 

...... , ... ir&+th""'( .. ""'1..~ . ...U 

.···. Fniiit~;&,%~~~· 

... , ;~~~:#~~~~ :: -~-~?iH~t~ 11

ru1J .•. .. .. ... .. ...... ... H.A ... im. .. 

::·.~:::~c~M .... ::·::: :::.:;~iik:: 

..••....••.•.•. j~:: .• ·· ··············· .. J'rMl1 ........ . lkt>J•m,o ...... ~.. ~~ 

&~···· ..... •·•••·· ...... · f~v& .. . 

Bonyan 

•. Rmy 

Fig. 10. 

12 

Stqw. 

. ...... 9'.-i#!Ut:!:M. .................. Bl•0<hr.rd 

...... ~"'°Ml .. !!1i:>m~"'"' 

............. ···· .. ·.~····· Aiill.""'1K ..... 

llaod,~i... . ... ~~1f··· 

Bibb, ....•.. ./~~ ....•. 

.. ..... ..... .. . '1M.wm.i-M .. ..................... ~~ ..... 

You will notice that the code equivalents are printed but their 

meanings are written in by hand. This was usually the case, and 

the reason is obvious: for economy in printing costs, because the 

printed code equivalents of plaintext items in cipher books belonging 

to the same series are identical; only their meanings change from one 

book to another, and of course, the transposition routes, their indicators, and other variables change from one book to another. I am 

fortunate in having six of these cipher books in my private collection, 

so that comparisons among them are readily made. The first feature 

to be noted is that the code equivalents are all good English dictionary words (or proper nouns), of not less than three nor more than 

seven (rarely eight) letters. A careful scrutiny shows that in the 

early editions the code equivalents are such as are not very likely to 

appear as words in the plaintext messages; but in the later editions, 

beginning with No. 12, more than 50% of the words used as code equivalents are such as might well appear in the plaintext of messages. For 

example, words such as AID, ALL, ARMY, ARTILLERY, JUNCTION, CONFEDERATE, etc., baptismal names of persons, and 

names of cities, rivers, bays, etc., appear as code equivalents. Among 

names used as code equivalents are SHERMAN, LINCOLN, 

THOMAS, STANTON, and those of many other prominent officers 

co~~F19nHIAL 46 
REF ID:A62856 

W. F. FRIEDMAN eot~FIBDHIAL 

and officials of the Union Army and the Federal Government, as 

well as of the Confederate Army and Government; and, even more 

intriguing, such names were employed as indicators for the number 

of columns and the routes used-the so-called "Commencement 

Words." It would seem that names and words such as those I've 

mentioned might occasionally have brought about instances where 

difficulty in deciphering messages arose from this source of confusion, 

but the literature doesn't mention them. I think you already realize 

why such commonly-used proper names and words were not excluded. 

There was, indeed, method in this madness. 

But what is indeed astonishing to note is that in the later editions 

of these cipher books, in a great majority of cases the words used as 

"arbitraries," differ from one another by at least two letters (for 

example, LADY, and LAMB, LARK and LAWN, ALBA and 

ASIA, LOCK and WICK, MILK and MINT), or by more than two 

(for example MYRTLE and MYSTIC, CARBON and CANCER, 

ANDES and ATLAS). One has to search for cases in which two 

words differ by only one letter, but they can be found if you search 

long enough for them, as, for example, QUINCY and QUINCE, 

PINE and PIKE, NOSE and ROSE. Often there are words with 

the same initial trigraph or tetragraph, but then the rest of the 

letters are such that errors in transmission or reception would easily 

manifest themselves, as, for example, in the cases of MONSTER 

and MONARCH, MAGNET and MAGNOLIA. All in all, it is 

important to note that the compiler or compilers of these cipher books 

had adopted a principle known today as the "two-letter differential," 

a feature found only in codebooks of a much later date. In brief, 

the principle involves the use, in a given codebook, of code groups 

differing from one another by at least two letters. This principle is 

employed by knowledgeable code compilers to this very day, not 

only because it enables the recipient of a message to detect errors in 

transmission or reception, but also to correct them. This is made 

possible if the permutation tables used in constructing the code 

words are printed in the codebooks, so that most errors can be corrected without calling for a repetition of the transmission. It is 

clear, therefore, that the compilers of these cipher books took into 

consideration the fact that errors are to be expected in Morse telegraphy, and by incorporating, but only to a limited extent, the principle of the two-letter differential, they tried to guard against the 

possibility that errors might go undetected. Had artificial 5-letter 

groups been used as code equivalents, instead of dictionary words, 

possibly the cipher books would also have contained the permutation 

tables. But it must be noted that permutation tables made their 

first appearance only about a quarter of a century after the Civil 

47 EOt~Fl0EtHIAL 
REF ID:A62856 

HISTORY OF CRYPTOLOGY 

War had ended, and then only in the most advanced types of commercial codes. 

There is, however, another feature about the words the compilers 

of these books chose as code equivalents. It is a feature that manifests real perspicacity on their part, and you probably already have 

divined it. A few moments ago I said that I would explain why, in 

the later and improved editions of these books, words which might 

well be words in plaintext messages were not excluded from the lists 

of code equivalents: it involves the fact that the basic nature of the 

cryptosystem in which these code equivalents were to be used was 

clearly recognized by those who compiled the books. Since the 

cryptosystem was based U{>On word transposition, what could be 

more confusing to a would-be cryptanalyst, working with messages 

in such a system, than to :find himself unable to decide whether a 

word in the cipher text of a message he is trying to solve is actually 

in the original plaintext message and has its normal meaning, or is a 

code word with a secret significance-or even a null, a non-significant word, a "blind" or a "check word," as those elements were called 

in those days? That, no doubt, is why there are, in these books, so 

many code equivalents which might well be "good" words in the 

plaintext messages. And in this connection I have already noted 

an additional interesting feature: at the top of each page devoted 

to indicators for signaling the number of columns or rows in the 

specific matrix for a message are printed the so-called "commencement words," or what we now call "indicators". Now there are 

nine such words, in sets of three, any one of which could actually be 

a real word or name in the plaintext message. Such words when 

used as indicators could be very confusing to enemy cryptanalysts, 

especially after the transposition operation. Here, for example, are 

the "commencement words" on page 5 of cipher book No. 9: Army, 

Anson, Action, Astor, Advance, Artillery, Anderson, Ambush, Agree; 

on page 7 of No. 10: Cairo, Curtin, Cavalry, Congress, Childs, 

Calhoun, Church, Cobb, etc. Moreover, in Nos. 1, 3, 4, 5, and 10 

the "line indicators," that is, the words indicating the number of 

horizontal rows in the matrix, are also words such as could easily be 

words in the plaintext messages. For example, in No. I, page 3, 

the line indicators are as follows: 

Address 1 Faith Assume 6 Bend 

Adjust 2 Favor Awake 7 Avail 

Answer 3 Confine Encamp 8 Active 

Appear 4 Bed Enroll 9 Absent 

Appeal 5 Beef Enough 10 Accept 

Note two things in the foregoing list: :first, there are variantsCOt~FIBD~flAL 48 
\ 

I 

I 

I 

~.\ 

REF ID:A62856 

W. F. FRIEDMAN eo~~FIBEtHIAL 

there are two indicators for each case; and second, the indicators are 

not in strict alphabetic sequence. This departure from strict alphabeticity is even more obvious in the pages devoted to vocabulary, a 

fact of much importance cryptanalytically. Note this feature, for 

example, in Fig. 10, which shows pages 14 and 15 of cipher book No. 

12. 

In this respect, therefore, these books partake somewhat of the 

nature of two-part or "randomized" codes, or, in British terminology, 

"hatted" codes. In the second lecture of this series the physical 

difference between one-part and two-part codes was briefly explained, 

but an indication of the technical cryptanalytic difference between 

these two types of codes may be useful at this point. Two-part codes 

are much more difficult to solve than one-part codes, in which both 

the plaintext elements and their code equivalents progress in parallel 

sequences. In the latter type, determination of the meaning of 

one code group quickly and rather easily leads to the determination 

of the meanings of other code groups above or below the one that has 

been solved. For example, in the following short but illustrative 

example, if the meaning of code group 1729 has been determined to 

be "then", the meaning of the code group 1728 could well be "the" 

and that of 

1728 - the 

1729 - then 

1730 - there 

7621 - the 

0972 - then 

1548 - there 

the code group 1730, "there". But in a two-part code, determining 

the meaning of the code group 0972 to be "then" gives no clue whatever as to the meaning of the groups 7621 or 1548. For ease in decoding 

messages in such a code there must be a section in which the code 

groups are listed in numerical sequence, and are accompanied by 

their meanings, which, of course, will be in a random sequence. The 

compilers of the USMTC cipher books must have had a very clear 

idea of what I have just explained, but they made a compromise of 

a practical nature between a strictly one-part and a strictly two-part 

code, because they realized that a code of the latter sort is twice as 

bulky as one of the former sort, besides being much more laborious 

to compile and check the contents for accuracy. The arrangement 

they chose wasn't too bad, so far as cryptosecurity was concerned. 

As a matter of fact, and speaking from personal experience in decoding a rather long message addressed to General Grant, I had a 

difficult time in locating many of the code words in the book, because of the departure from strict alphabeticity. I came across that 

message in a workbook in my collection, the workbook of one of the 

important members of the USMTC-none other than our friend 

49 CONF19HHIAL 
REF ID:A62856 

COt~FIBEtHIAL HISTORY OF CRYPTOLOGY 

Plum, from whose book, The Military Telegraph during the Civil War, 

comes much of the data I've presented in this lecture. On the flyleaf of Plum's workbook there appears, presumably in his own handwriting, the legend "W.R. Plum Chf Opr with Gen. G. H. Thomas". 

Here's one of the messages he enciphered in cipher book No. 1, the 

book in which, he says, more important telegrams were sent than in 

any other: 

-¥ 9 I ., ~ A.. .r ·' " ~ 

I .n.•1 ,, ..... ....,,,_ - -L · . ..,,_j) -- - - ~- ., A "• ,_ ~ F~•'' n 

Si. IJ w . , I...~., .... y, ,, .,. ~-·· .Jo ,_ .. I"'- .y.. rr<- , .• - I " ""'· •.1,.11_' l , 

-"w"..i(. ~- ~-- "#: ~- (a,, 

-s~7 6 

I - 'J-. ', "'"'"· I 

~,.,._,, 

~. - r. -~ ,, , 1 ..... 

~ v..1.1_ r, I' 

~ ~ (..__!.-- a . l 

3 A...o 

t·r...JJJ. 

- I 

Fig. 11. 

Note how many "arbitraries" appear in the plaintext message, that 

is before transposition. After transposition the melange of plaintext, 

code words, indicators and nulls makes the cryptogram mystifying. 5 

And yet, was the system as inscrutable as its users apparently thought? 

It is to be remembered, of course, that messages were then transmitted by wire telegraphy, not by radio, so that enemy messages could 

be obtained only by "tapping" telegraph lines or capturing couriers 

or headquarters with their files intact. Opportunities for these 

methods of acquiring enemy traffic were not frequent, but they did 

occur from. time to time, and in one case a Confederate signalman 

hid in a swamp for several weeks and tapped a Federal telegraph 

line, obtaining a good many messages. What success, if any, did 

Confederate cryptanalysts have in their attempts to solve such 

USMTC cryptograms as they did intercept? We shall try to answer 

this question in due time. 

6 In searching for a good example my eye caught the words "Lincoln shot" 

at the left of the matrix and I immediately thought that the message had to 

do with Booth's assassination of the President. But after hurriedly translating 

the message and finding nothing in it having anything to do with the shooting 

it occurred to me to look up the indicators for a matrix of six rows and eight 

columns. They turned out to be LINCOLN (message of 8 columns), SHOT 

(6 rows). The word SMALL beneath the "Lincoln shot" is a variant for SHOT, 

also meaning "6 rows". 

EOt~FIBENTIAL 50 
W. F. FRIEDMAN C0~4F19nHIAL 

As indicated earlier, there were no competing signal organizations 

in the Confederacy as there were on the Union side. There was 

nothing at the center of government in Richmond or in the combat 

zone comparable to the extensive and tightly-controlled civilian 

military telegraph organization which Secretary Stanton ruled with 

such an iron hand from Washington. Almost as a concomitant, it 

would seem, there was in the Confederacy, save for two exceptional 

cases, one and only one officially-established cryptosystem to serve 

the need for protecting tactical as well as strategic communications, 

and that was the so-called Vigenere Cipher, which apparently was 

the cipher authorized in an official manual prepared by Captain J. H. 

Alexander as the partial equivalent of Myer's Manual of Signals. 

You won't find the name Vigenere in any of the writings of contemporary signal officers of either the North or the South. The signalmen of those days called it the "Court Cipher", this term referring 

to the system in common use for diplomatic or "court" secret communications about this period in history. It is that cipher which 

employs the so-called Vigenere Square with a repeating key. 6 Here 

is the square which Plum calls the "Confederate States Cipher Key" 

and which is followed by his description of its manner of employment. (See figs. 12a and12b.) 

There are certain comments to be made on the sample messages. 

In the first place, note that in the first message certain words are 

left unenciphered; in the second place, in both the first and second 

messages, the ciphers retain and clearly show the lengths of the words 

which have been enciphered. Both of these faulty practices greatly 

weaken the security of ciphers because they leave good clues to their 

contents and can easily result in facilitating solution of the messages. 

We know today that cipher messages must leave nothing in the clear. 

Even the address and the signature, the date, time and place of 

origin, etc., should if possible be hidden; and the cipher text should 

be in completely regular groupings, first, so as not to disclose the 

lengths of the plaintext words, and second, to promote accuracy in 

transmission and reception. 

So far as my studies have gone, I have not found a single example 

of a Confederate Vigenere cipher which shows neither of these two 

fatal weaknesses. The second of the two examples is the only case 

I have found in which there are no unenciphered words in the text 

of the message. And the only example I have been able to find in 

6 A keyword is employed to change the alphabets cyclically, thus making 

the cipher what is called today a periodic or multiple-alphabet cipher controlled by the individual letters of a key, which may consist of a word, a phrase, or 

even of a sentence, repeated as many times as necessary. 

51 EOt~FIDnHIAL 
!' 

JI 

Ii 

Ii' 

fL 

'i' 

1, " 

I 

REF ID:A62856 

EOt~FIBU~flAL HISTORY OF CRYPTOLOGY 

88 THE MILITARY TELEGRAPH DURING THE 

CONFEDERATE ST.ATES CIPHER KEY. 

26 25 24 23 22 21 20 19 18 17 16 15 14 18 12 11 10 9 8 7 6 5 4 8 2 1 1 a b c d e f g h i j k Imn 0 p q r 8 tuvwxyz 2 b c d e f g h j k I Dl D 0 p q r s t u v w x y z a 3 c d e f g h i j klmno p q r s t u vw x y z a b 4 d e f g h j k I m n o p q r s u v w x y z a b c rr e f g h j k I m n o p q r s u v w x y z a b c d 6 f g h j k I m n 0 p q r B t u v w x y z a b c d e 7 g h i j k Im n 0 p q r s t u v w x y z a b c d e f 8 h i j k lmn 0 p q r B uvw x y z a b c d e f' g 9 I j k I m n o p q r s u v w x y z a b c d e f' g h 10 j k I m n o p q r s u v w x y z a b c d e f g h 11 k I m n 0 p q r s t u v w x y z a b c d e f g h j 12 I m n o p q r s t u v w x y z a b c d tl f g h j k 13 m n o p q r s t u v w x y z a b c d e f g h j k I 14 n 0 p q r s t u v w x y z a b c d e f g h j k I m 115 0 p q r s t u v w x y z a b c d e f g h j k lmn 16 p q r s t u v w x y z a b c d e f g h j k I m n 0 17 q r 8 t u v w x y z a b c d e f' g h j k I m n o p 18 r s t u v w x y z a b c d e f g h j k Imn 0 p q 19 8 t u v w x y z a b c d e f g h j k lmn 0 p q r 20 t u v w x y z 8 b c d e f g h j k l m n 0 p q r s 21 u v w x y z a b c d e f g h j k lmn o p q r s t 22 v w x y z a b c d e f' g h j k I m n o p q r s t u 23 w x y z a b c d e f g h j k I mn 0 p q r s t u v 24 x y z a b c d e f g h 1 J k lmn 0 p q r 8 t u v w 26 y z a b c d e f g h i j k I m n 0 p q 26 z b r s t u vw x a c d e f g b i j k I mn 0 p q r 8 t u v w x y 

Key Worda.-Complete Victory. Manchester Bluff. 

To put into cipher the first message, which is put up by using 

"Manchester Bluff" as the key, and the second by the key term, 

"Complete Victory," find at the left-hand side of the table the 

first letter of the first word to be ciphered, and at the top of the 

table, the first letter of the key term. At the junction of the 

columns in which these letters are so found, will be seen the 

arbitrary letter which is to be used in lieu of the real one at the 

left. Continue in this way with each successive letter of the 

message and key term, repeating on the latter tiJI finished. Thus, 

"Sherman is victorious," put in cipher by using the first key, 

Would r d h b th 't l C-o-m-p-1-e-t- e v-i-<:-t-o- ea , as s own y e cap1 a s, u v Q G x E G )I N DK v H 

Fig. 12-A. 

C0~4Fl0EtHIAL 52 
REF ID:A62B56 

w. F. FRIEDMAN CONFIBEt~'flAL 

F~ ~""t:!rJt Of course, any change in the key word, term 

or phrase changes the arbitrarics, and if neither the real 

message nor the key is known, it would be somewhat vexatious 

working it out, unless there were some such suggestive words 

as occur in Davis's message above, which indicate the ciphered 

words very clearly ; e. g., "By which you may effect" ~ ~1;.~~~f~ ~ 

" ,, hj opg kwm..ct . • 0 

above that part of the riv• r. Tins meanmg occurred to the 

author, at flr,;t sight, and doubtless would to any one familiar 

with military atti1ir' in that section. Having guessed real words, it 

is very easy to work out the letters of the' key. The following 

two important ciphers were tram•mitte<l as divided below; i. e., 

each w01·1! wa-; ·'<·nt ·'<•p11mtl'ly. not all mixe1l, ns in the Pclllberton cipher. This divi.-ion does not faeilitatc translation hy the 

key at ull, hut materially a>,i4s without it, and \\·as, therefore, 

bad pmctice. "\\"<'give hc·low, C'aeh llles,.;n,ze, with its trnn.•ltttfon, 

because these tcll'grams W<·re very important. • T.hc l"IH"ious 

reader may, at hi.• lei>urc, hy u.,ing the )H·y ho11rd, study out the 

key terms, one of which will he found cntirPly new and quite 

apropos, in the light of what ,;p<'e<lily followed. 

CONFEDERATE STATES OF Al!F.RICA, :\[n.lrARY TELEGRAPH. Dated 

Head-quarters, F<>bruary 25, 18G.'i. Recoi\'ed at Richmoml,Va., 

12:25 minutes, A. lf. 

To Hox. J.C. ll1tECKEXrt1J>GE, Sec'y of \Var: - I recommend 

that the tsysmec fn c1011twp rfat\"\'mp uhwaqbqtm exfl"Xj and iswacijru 

ktmtl are not of immediate necessity, uv kpgfmbpgr mpc thnlfl 

should be l1114hts1>. (Signed) R. E. LEi,:, 

TRAXSLATIOY.-I recommend that t.he remoi·rrl qfp1d1!ic property, 

macltiner.i;, stores and arclii1Jes 'll'ldc!t are not of immediate uecessity, 

be commellced. All po1cder should be secured. 

HEAil-QL"ARTERS C. S. AirnIEs, March 24, 18G5. 

GEY. E. Kmny SmTn, comdg. Trans-!IIiss. Dept., Gen.:-Vvq 

ecilmympm rvcng ui lhnmni<les kfch kdf wasptf us tfcfsto abxc 

bjx azjkhmgjsiimivbceq qb rule! ueisu ht kfg auhd egh opcm mfs 

urajwh xryrncoci yu ddclxtrnpt in iejqkpxt es vvjau mvrr twhtc abxc 

iu eoieg o rdrgx en ucr P'" ntiptyxec rqrnriyyh r;:·7.<j rspz rksjcph,pta]\: 

rsp ekez raecdstrzpt mzmseb acgg nsfqvvf me kfg srnhe ftrf wb 

mvv kkge pyh fefm ckfrlisytyxl xj jtbbx rq htxd wbhz awvv fd acgg 

avxwzV\' yciag oe nzy fet lgxa scuh. 

I am most respectfully your obdt. servt., 

(Signed) R. E. LEE. 

TRANSLATION.-Gen.: The President deems it advisable that 

you should be charged with the military operations on both b11nks 

of the Miss., and that you should endeavor as promptly as possible to 

cross that river with as large a force as may be prudently withdrawn 

from your present Dept. You will accordingly extend your oommand 

to the ea;t bank of the Miss., and make arrangements to bring to 

tbi · side such of your present force as you may deem best. 

I am mo;t respectfully your obedient servant. 

Fig. 12-B 

53 CONFIDHHIAL 
REF ID:A62856 

COl'm9HHIAL HISTORY OF CRYPTOLOGY 

which word lengths are not shown 

of the following message: 

GEN. J.E. JOHNSTON, JACKSON: 

Vicksburg, Dec. 26, 1862. 

I prefer oaavvr, it has reference to xhvkjqchffabpzelreqpzwnyk to 

prevent anuzeyxswstpjw at that point, raeelpsghvelvtzfautlilaslt 

lhifnaigtsmntlfgccajd. 

(Signed) J. C. PEMBERTON 

' Lt. Gen. Comdg. 

Even in this case there are unenciphered words which afforded a 

clue which enabled our man Plum to find the key and solve the message. It took some time, however, and the story is worth telling. 

According to Plum, the foregoing cipher message was the very :first 

one captured by USMTC operators, and it was obtained during the 

siege of Vicksburg, which surrendered on 4 July 1863. But note the 

date of the message: 26 December 1862. What was done with the 

captured message during the months from the end of December 1862 

to July 1863? Apparently nothing. Here is what Plum reports: 

What efforts General Grant caused to be inade to unravel this message, we know not. It was not until October, 1864, that it and others 

came into the hands of the telegraph cipherers, at New Orleans, for 

translation .... 

The New Orleans operators who worked out this key (Manchester 

Bluff) were aided by the Pemberton cipher and the original telegram, 

which was found among that general's papers, after the surrender of 

Vicksburg; also by the following cipher dispatch, and one other. 

Plum gives the messages involved, their solution, and the keys, 

the latter being the three cited above. It would seem that if the 

captured Pemberton message had been brought to General Grant's 

attention and he did nothing about it, he was not much interested in 

intelligence. Secondly, the solution of the Pemberton message and 

the others apparently took some time, even though there was one 

message with its plain text (the Pemberton message) and two messages 

not only with interspersed plaintext words but also with spaces 

showing word lengths. But Plum does not indicate how long it took 

for solution. Note that he merely says that the messages came into 

the hands of the telegraph cipherers in October 1864; he does not tell 

when solution was reached. 

In the various accounts of these Confederate ciphers there is one 

and only one writer who makes a detailed comment on the two fatal 

practices to which I refer. A certain Dr. Charles E. Taylor, a Confederate veteran (in an article entitled "The Signal and Secret Service of the Confederate States", published in the Confederate Veteran, 

54 
W. F. FRIEDMAN EOt~FIBEt~TIAL 

Vol. XL, Aug-Sept 1932), after giving an example of encipherment 

according to the "court cipher" says: 

It hardly needs to be said that the division between the words of 

the original message as given above was not retained in the cipher. 

Either the letters were run together continuously or breaks, as if for 

words, were made at random. Until the folly of the method was 

revealed by experience, only a few special w~rds in a meBSage were put 

into cipher, while the rest was sent in plain language. Thus ... I 

think it may be said that it was impoBSible for well prepared cipher 

to be correctly read by any one who did not know the key-word. Sometimes, in fact, we could not decipher our own messages when they came 

over telegraph wires. As the operators had no meaning to guide them, 

letters easily became changed and portions, at least, of meBBages 

rendered unmeaningly (sic) thereby. 

Frankly, I don't believe Dr. Taylor's comments are to be taken as 

characterizing the practices that were usually followed. No other 

ex-signalman who has written about the ciphers used by the Confederate Signal Corps makes such observations and I think we must 

simply discount what Dr. Taylor says in this regard. 

It would certainly be an unwarranted exaggeration to say that the 

two weaknesses in the Confederate cryptosystem cost the Confederacy the victory for which it fought so mightily, but I do feel warranted at this moment in saying that further research may well show 

that certain battles and campaigns were lost because of insecure 

cryptocommunications. 

A few moments ago I said that, save for an exception or two, 

there was in the Confederacy one and only one cryptosystem to serve 

the need for secure tactical as well as strategic communications. 

One of these exceptions concerned the cipher used by General Beauregard after the battle of Shiloh (8 April 1862). This cipher was 

purely monoalphabetic in nature and was discarded as soon as the 

official cipher system was prescribed in Alexander's manual. It is 

interesting to note that this was done after the deciphered message 

came to the attention of Confederate authorities in Richmond via a 

northern newspaper. It is also interesting to note that the Federal 

War Department had begun using the route cipher as the official 

system for USMTC messages very promptly after the outbreak of 

war, whereas not until 1862 did the Confederate States War Department prepare an official cryptosystem, and then it adopted the 

"court cipher." 

The other exception involved a system used at least once before 

the official system was adopted and it was so different from the 

latter that it should be mentioned. On 26 March 1862, the Confederate States President, Jefferson Davis, sent General Johnston by 

55 COt~FIBEtHIAL 
REF ID:A62856 

EO~~FIBEt~TIAL HISTORY OF CRYPTOLOGY 

special messenger a dictionary, with the following accompanying 

instruction: 7 

I send you a dictionary of which I have the duplicate, so that you 

may communicate with me by cipher, telegraphic or written, as follows: 

First give the page by its number; second, the column by the letter L, 

M or R, as it may be, in the left-hand, middle, or right-hand columns; 

third, the number of the word in the column, counting from the top. 

Thus, the word junction would be designated by 146, L, 20. 

The foregoing, as you no doubt have already realized, is one of the 

types of cryptosystems used by both sides during the American 

Revolutionary Period almost a century before, except that in this 

case the dictionary had three columns to the page instead of two. 

I haven't tried to find the dictionary but it shouldn't take long to 

locate it, since the code equivalent of the word "junction" was given: 

146, L, 20. Moreover, there is extant at least one fairly long message, with its decode. How many other messages in this system there 

may be in National Archives I don't know. 

Coming back now to the "court cipher," you will probably find it 

just as hard to believe, as I find it, that according to all accounts 

three and only three keys were used by the Confederates during the 

three and a half years of warfare from 1862 to mid-1865. It is true 

that Southern signalmen make mention of frequent changes in key 

but only the following three are specifically cited: 

1) COMPLETE VICTORY 

2) MANCHESTER BLUFF 

3) COME RETRIBUTION. 

It seems that all were used concurrently. There may have been a 

fourth key, IN GOD WE TRUST, but I have seen it only once, and 

that is in a book explaining the "court cipher". Note that each of 

the three keys listed above consists of exactly 15 letters, but why 

this length was chosen is not clear. Had the rule been to make the 

cipher messages contain only 5-letter groups, the explanation would 

be easy: 15 is a multiple of 5 and this would be of practical value in 

checking the cryptographic work. But, as has been clearly stated, 

disguising word lengths was apparently not the practice even if it 

was prescribed, so that there was no advantage in choosing keys 

which contain a multiple of 5 letters. And, by the way, doesn't the 

key COME RETRIBUTION sound rather ominous to you even 

these days? 

Sooner or later a Confederate signal officer was bound to come up 

7 Battles and Leaders of the Civil War, New York: The Century Co., 1884, 

Vol. I, p. 581. 

co~menHIAL 56 
REF ID:A62856 

W. F. FRIEDMAN cor-mennv,L 

with a device to simplify ciphering operations, and a gadget devised 

by a Captain William N. Barker seemed to meet the need. In 

Myer's Manual there is a picture of one form of the device, shown 

here in Fig. 13. I don't think it necessary to explain how it worked, 

for it is almost self-evident. Several of these devices were captured 

during the war, one of them being among the items in the NSA 

Museum (Fig. 14). This device was captured at Mobile in 1865. All 

it did was to mechanize, in a rather inefficient manner, the use of the 

Vigenere Cipher. But here's a photograph, Fig. 15, of the one found 

in the office of Confederate Secretary of State Judah P. Benjamin 

after the capture of Richmond. In this picture the Vigenere Square 

(wrapped around the revolvable central shaft) is seen very clearly. 

Cipher Beel. 

Fig. 13. 

Fig. 14. 

57 co~~FIBEt~TIAL 
REF ID:A62856 

EOUFIBDHIAL HISTORY OF CRYPTOLOGY 

Fig. 15. 

How many of these devices were in exist.ence or use is unknown, 

for their construction was an individual matt.er-apparently it was 

not an item of regular issue to members of the corps. 

In practically every account of the codes and ciphers of the Civil 

War you will find references to ciphers used by Confederat.e secret 

service agents engaged in espionage in the North as well as in Canada. 

In particular, much att.ention is given to a set of letters in cipher, 

which were int.ercepted by the New York City Postmast.er and which 

were involved in a plot to print Confederat.e currency and bonds. 

Much ado was made about the solution of these ciphers by cipher 

operators of the USMTC in Washington and the consequent breaking up of the plot. But I won't go into these ciphers for two reasons. 

First, the alphabets were all of the simple monoalphabetic type, a 

total of six altogether being used. Since they were composed of 

a different series of symbols for each alphabet, it was possible to compose a cipher word by jumping from one series to another without 

any external indication of the shift. However, good eyesight and a 

bit of patience were all that was required for solution in this case 

because of the inept manner in which the syst.em was used: whole 

words, sometimes several successive words, were enciphered by the 

same alphabet. But the second reason for my not going into the 

story is that my friend and colleague of my NSA days Edwin C. 

Fishel, has done some research among the records in our National 

Archives dealing with this case and he has found something which 

is of great int.erest and which I feel bound to leave for him tot.ell at 

some future time, as that is his story, not mine. 

co~mBDHIAL 58 
REF ID:A62856 

W. F. FRIEDMAN EOt~FIBEt~flAL 

lfk~Thcni·:Fu m.1 K U1)'01·111~:<n · \· \r x y z 

!1 ~\ Bt 'DE Fm I I.I K L'.\I '\\1 H'(}l~~Tl. \ \\" \ YZ.\ 

llBCDEFliill.JKUIXO!'t,!I::'TI \ WX\/ .. \ 1: 

'iCJlEI"fi 111.J K L'i \1 ll'<JH:-'Tl. \ \\':\Yi'..\ f!(' 

. JlEl·'tjilf.11\U! .\"O!'tJH:-i'tTnrx YZ.\ (;! fl 

I·:FHlll.!KtllXOl't/l::~n \"\\'XYZ.\l!t I1E 

F<;Ifl.Jl\:L'.\I Xt lf'i~n.<rr r \\" x YZ;\ fll 'I •EF n111.JKL'.\IXOl'l~H:'Tl nrx YI..\ fll 'PEl'fi 

!il.JKL'..\lXOl'1,11:.<rt \'\\ X :"/''..\ ll< "flFHili 1 I .I K L)f :Xt l!'t)l::-:n. \" \\' \ YZ.\ Pc 'flEFI; 11 ; 

'.JK UIXOl 0

Q:t...:T1. \" \\ X YZ.\ IH '!fU'': II !.I 

K L'.\I ~Ol'l/l:.··q !' r \r \. \ Z.\ 1:1 'll l:Ft; ll i.l I\ 

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. MXCff<Jlif'"JT nr :\ )L\ I:' 'I>l:l't ;(1f.J !~ L'.\1 XOl'IJf~;-:·rr r \\' \ YZ.\ l!i '(!EH ;HJ.I I\ UI x 

OPQH:'1T nr \ YZ.\ f;C 'JIEFI d 11.1 l\ Uf x (I 

PQH!"Tt ·nrx YZ.\ Ill 'HEFl;lll.IKUI \I II' 

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H:-'TI" \"\\' XYZ.\ JH 'l>EFI :111.11.; l.,f >:1 ;f 'il I: 

;-: 'lT\'W x YZ.\ B• ·111·:n ill I.I I\ DI .X< lf'I w·: 

Tl. rw x YZABCllEFlllfl.1 K Ul:\Oi 't:t;:-'r 

, l' \ \\" X YZ.\ rn 'PEFC 111.11\ L:\l \" 0 l'ill:.'TI. 

'nrx YZ.\lWl>l·:Fti 111.IKLMXOl'•jll:'TI. \ I wx y Z.\ fl( 'llEFi; ff I.! I\ DI:\ Pl'•JH:-T!. \' \\ 

l X\'Z.\ Bl'l>EF<Jlfl.11\ D! Sol 't[f:;...;'4 l \'\\" X 

i: YZ.\H< 'Hl·:rn Ill.I I\ L'.\I ~o l'•~i::-n · ,. \\ x r 

!17.AJWl>EFflll I.I KC\I :\t l{'<JB:-' 11 · \ \\" X YZ 

Fig. 16. 

Photographs from which Figs. 15 and 16 were reproduced were kindly supplied me by my friend William H. Price, of NSA. 

59 co~~F19EtHIAL 
;: 

I

ii 

ii 

1:. 

I 

i 

REF ID:A62856 

COt~FIBBHIAL HISTORY OF CRYPTOLOGY 

So very fragmentary was the amount of cryptologic information 

known to the general public in these days that when there was found 

on John Wilkes Booth's body a cipher square which was almost identical with the cipher square which had been mounted on the cipher 

reel found in Confederate Secretary of State Judah P. Benjamin's 

office in Richmond, the Federal authorities in Washington attempted to prove that this necessarily meant that the Confederate 

leaders were implicated in the plot to assassinate Lincoln, and had 

been giving Booth instructions in cipher. Fig. 16 is a picture of the 

cipher square found on Booth, and also in a trunk in his hotel room 

in Washington. 

The following is quoted from Philip Van Doren Stern's book entitled Secret Missions of the Civil War (Rand McNally and Co., New 

York, 1951, p. 320): 

Everyone in the War Department who was familiar with cryptography knew that the Vigenere was the customary Confederate cipher 

and that for a Confederate agent (which Booth is known to have 

been) to possess a copy of a variation of it meant no more than if a 

telegraph operator was captured with a copy of the Morse Code. 

Hundreds-and perhaps thousands of people were using the Vigenere. 

But the Government was desperately seeking evidence against the 

Confederate leaders so they took advantage of the atmosphere of 

mystery which has always surrounded cryptography and used it to 

confuse the public and the press. This shabby trick gained nothing, 

for the leaders of the Confederacy eventually had to be let go for 

lack of evidence. 

To the foregoing I will comment that I doubt very much whether 

"everyone in the War Department who was familiar with cryptography knew that the Vigenere was the customary Confederate 

cipher." Probably not one of them had even heard the name Vigenere or had even seen a copy of the table, except those captured in 

operations. I doubt whether anyone on either side even knew that 

the cipher used by the Confederacy had a name; or least of all, that 

a German Army reservist named Kasiski, in a book published in 

1863, showed how the Vigenere cipher could be solved by a straightforward mathematical method. 

I have devoted a good deal more attention to the methods and 

means for cryptocommunications in the Civil War than they deserve, 

because professional cryptologists of 1961 can hardly be impressed 

either by their efficacy from the point of view of ease and rapidity 

in the cryptographic processing, or by the degree of the technical 

security they imparted to the messages they were intended to protect. 

Not much can be said for the security of the visual signaling systems 

used in the combat zone by the Federal Signal Corps for tactical 

purposes, because they were practically all based upon simple monoCOt~FIBEtHIAL 60 
l 

REF ID:A62856 

W. F. FRIEDMAN EOt~FIE>Et~TIAL 

alphabetic ciphers, or variations thereof, as for instance, when whole 

words were enciphered by the same alphabet. There is plenty of 

evidence that Confederate signalmen were more or less regularly 

reading and solving those signals. What can be said about the 

security of the route ciphers used by the USMTC for strategic or 

high command communications in the zone of the interior? It has 

already been indicated that, according to accounts by ex-USMTC 

men, such ciphers were beyond the cryptanalytic capabilities of Confederate cryptanalysts, but can we really believe that this was true? 

Considering the simplicity of these route ciphers and the undoubted 

intellectual capacities of Confederate officers and soldiers, why 

should messages in these systems have resisted cryptanalytic attack? 

In many cases the general subject matter of a message and perhaps 

a number of specific items of information could be detected by quick 

inspection of the message. Certainly, if it were not for the so-called 

"arbitraries" the general sense of the message could be found by a 

few minutes work, since the basic system must have been known 

through the capture of cipher books, a fact mentioned several times 

in the literature. Capture of but one book (they were all generally 

alike) would have told Confederate signalmen exactly how the system 

worked and this would naturally give away the basic secret of the 

superseding book. So we must see that whatever degree of protection these route ciphers afforded, message security depended almost entirely upon the number of "arbitraries" actually used in practice. A review of such messages as are available shows wide divergencies in the use of "arbitraries". In any event the number actually 

present in these books must have fallen far short of the number 

needed to give the real protection that a well-constructed code can 

give. Thus it seems to me that the application of native intelligence, 

with some patience, should have been sufficient to solve USMTC messages-or so it would be quite logical to assume. That such an assumption is well warranted is readily demonstrable. 

It was, curiously enough, at about this point in preparing this 

lecture that Mr. Edwin C. Fishel, whom I have mentioned before, 

gave me just the right material for such a demonstration. In June of 

1960, Mr. Fishel had given Mr. Phillip Bridges, who is also a member 

of NSA and who knew nothing about the route ciphers of the USMTC, 

the following authentic message sent on 1 July 1863 by General 

George G. Meade, at Harrisburg, Pennsylvania, to General Couch at 

Washington. (See fig. 17.) 

It took Mr. Bridges only a few hours, five or six, to solve the 

cryptogram, and he handed the following plain text to Mr. Fishel: 

61 eo~mBHHIAL 
REF ID:A62856 

co~meEtHIAt HISTORY OF CRYPTOLOGY 

Fig. 17. 

Thomas been it------(Nulls) 

For Parson. I shall try and get to you by tomorrow morning a reliable gentleman and some seouts who are acquainted with a country 

you wish to know of. Rebels this way have all concentrated in direction of Gettysburg and Chambersburg. I occupy Carlisle. Signed 

Optic. Great battle very soon. tree much deal----(Nulls) 

The foregoing solution is correct, save for one pardonable error: 

"Thomas" is not a "null" but an indicator for the dimensions of the 

matrix and the route. "Parson" and "Optic" are code names and I 

imagine that Mr. Bridges recognized them as such but, of course, he 

had no way of interpreting them, except perhaps by making a careful study of the events and commanders involved in the impending 

action, a study he wasn't called upon to undertake. 

The foregoing message was enciphered by Cipher Book No. 12, in 

which the indicator THOMAS specifies a "Message of 10 lines and 

5 columns". The route was quite simple and straightforward: 

"Down the 1st (column), up the 3rd; down the 2nd; up the 5th 

down the 4th." 

It is obvious that in this example the absence of many "arbitraries," 

made solution a relatively easy matter. What Mr. Bridges would 

have been able to do with the cryptogram had there been many of 

them is problematical. Judging by his worksheets, it seemed to me 

CONFIDENflAL 62 
l 

I 

I 

I 

f 

REF ID:A62856 

w. F. FRIEDMAN co~mBEtHIAL 

that Mr. Bridges did not realize when he was solving the message 

that a transposition matrix was involved; and on questioning him on 

this point his answer was in the negative. He realized this only 

later. 

A minor drama in the fortunes of Major General D. C. Buell, one 

of the high commanders of the Federal Army, is quietly and tersely 

outlined in two cipher telegrams. The first one, sent on 29 September 1862, from Louisville, Kentucky,. was in one of the USMTC 

cipher books, and was externally addressed to Colonel Anson Stager, 

head of the USMTC, but the internal addressee was Major General 

H. W. Halleck, "General-in-Chief" [our present day "Chief of Staff"]. 

The message was externally signed by William H. Drake, Buell's 

cipher operator, but the name of the actual sender, Buell, was indicated internally. Here's the telegram: 

COLONEL ANSON STAGER, Washington: 

Austria await I in over to requiring orders olden rapture blissful for 

your instant command turned and instructions and rough looking further shall further the Camden me of ocean September poker twenty I 

the to I command obedience repair orders quickly pretty Indianapolis 

your him accordingly my fourth received 1862 wounded nine have 

twenty turn have to to to alvord hasty. 

WILLIAM H. DRAKE 

Rather than give you the plain text of this message, perhaps you 

would like to work it out for yourselves, for with the information 

you've already received the solution should not be difficult. The 

message contains one error, which was made in its original preparation: one word was omitted. 

The second telegram, only one day later, was also from Major 

General Buell, to Major General Halleck, but it was in another 

cipher book-apparently the two books involved were used concurrently. Here it is: 

GEORGE C. MAYNARD, Washington: 

Regulars ordered of my to public out suspending received 1862 

spoiled thirty I dispatch command of continue of best otherwise worst 

Arabia my command discharge duty of my last for Lincoln September 

period your from sense shall duties the until Seward ability to the I a 

removal evening Adam herald tribune. 8 

PHILIP BRUNER 

As before, I will give you the opportunity to solve this message 

8 A curious coincidence--or was it a fortuitous foreshadowing of an event far 

in the future?-can be seen in the sequence of the last two words of the cipher 

text. The message is dated September 30, 1862; the New York Herald and 

the New York Tribune combined to make the New York Herald-Tribune on 

March 19, 1924-62 years later! 

63 CO~lf:IQ~~~JIAL 
REF ID:A62856 

EOt~FIBDOIAL HISTORY OF CRYPTOLOGY 

,Y ' 

a ',;f~'7 

-~' ,,.c;r ,,,,-;_,.- ~ # " 

Fig. 18-A. 

C:Oti!f F16Eti!fTIAL 64 
REF ID:A62856 

W. F. FRIEDMAN C0~4FIDnHlt\L 

Greensboro N.C. 

April ll 1865 

Benaja 11 Hd Q near R. G. 

Genl J. E. Johnston 

A scout (reports?) tha.t Genl Lee 

uiDvvswvzFx-mqs-EGAzoxH W - P J M - T z A t • near to appomattox Court 

house yesterday No official intelligence of the 

event D i F .. x y i k v - q T - F B B H Y G -

F A S D • J H i • L P 0 u B • As to result Gen H. H. 

Walker is ordered Y W F T .. W S K T M T - B X z S -

Gq•XAmE-CHT-iu-AKMSAuPuVFLet me hear from you there- I will ha.ve need to 

see you to confer as to future action. The above 

is my telegram of' yesterday which is repeated as 

requested. 

18-B. 

65 

Jeffn Davis 

Of'f'icial 

Burton Harrison 

Private Secty 

co~mBEt~flAL 
REF ID:A62856 

co~monrn1,L HISTORY OF CRYPTOLOGY 

for yourselves. (At the end of the next lecture I shall present the 

plain text of both messages.) 

Figure 18 is a photograph of an important message which you 

may wish to solve yourself. It was sent by President Jefferson 

Davis to General Johnston, on a very significant date, 11 April 

1865. * For ease in working on it I give also a transcription, since 

the photograph is very old and in poor state. I believe that this 

message does not appear in any of the accounts I've read. 

It is time now to tell you what I can about the success or lack of 

success which each side had with the cryptograms of the other side. 

I wish there were more information on this interesting subject than 

what I am about to present. Most of what sound information there 

is comes from a book by a man named J. Willard Brown, who served 

four full years in the Federal Army's Signal Corps. The book is 

entitled The Signal Corps, U.S.A. in the War of the Rebellion, published 

in Boston in 1896 by the U.S. Veteran Signal Corps Association. In 

his book Brown deals with the cryptanalytic success of both sides. 

First, let's see what the Union signalmen could do with rebel ciphers. 

Here are some statements he makes (p. 214): 

The first deciphering of a rebel signal code of which I find any record was that made by Capt. J. S. Hall and Capt. R. A. Taylor, reported Nov. 25, 1862. Four days later, Maj. Myer wrote to Capt. 

Cushing, Chief Signal Officer, Army of the Potomac, not to permit 

it to become public "that we translate the signal messages of the rebel 

army". 

April 9, 1863, Capt. Fisher, near Falmouth, reported that one of his 

officers had read a rebel message which proved that the rebels were in 

possession of our code. The next day he was informed that the rebel 

code taken (from) a rebel signal officer was identical with one taken 

previously at Yorktown. 

He received from Maj. Myer the following orders: 

"Send over your lines, from time to time, meBBages which, if it is in 

the power of the enemy to decipher them, will lead them to believe 

that we cannot get any clew to their signals." 

"Send also occasionally messages untrue, in reference to imaginary 

military movements, as for instance,-"The Sixth Corps is ordered to 

reinforce Keyes at Yorktown." 

Undoubtedly, what we have here are references to the general 

cipher system used by the Confederates in their electric-telegraph 

communications, for note the expression "Send over your lines". 

This could hardly refer to visual communications. Here we also 

have very e~rly instances, in telegraphic communications, of what we 

call cover and deception, i. e., employing certain ruses to try to hide 

the fact that enemy signals could be read, and to try to deceive him 

*I should warn you that it contains several errors! 

eor~FIE>EtHIAL 66 
t 

REF ID:A62856 

w. F. FRIEDMAN CONFIBE~UIAL 

by sending spurious messages for him to read, hoping the fraud will 

not be detected. 

Brown's account of Union cryptanalytic successes continues (p. 

215): 

In October, 1863, Capt. Merrill's party deciphered a code, and in 

November of the same year Capt. Thickstun and Capt. Marston deciphered another in Virginia. , 

Lieut. Howgate and Lieut. Flook, in March, 1864, deciphered a code 

in the Western Army, and at the same time Lieut. Benner found one 

at Alexandria, Virginia. 

Capt. Paul Babcock, Jr., then Chief Signal Officer, Department of 

the Cumberland, in a letter dated Chattanooga, Tennessee, April 26, 

1864, transmitting a copy of the rebel signal code, says: 

Capt. Cole and Lieut. Howgate, acting Signal Officers, 

occupy a station of communication and observation on White 

Oak Ridge at Ringgold, Ga .... On the 22nd inst. the rebels 

changed their code to the one enclosed, and on the same day 

the above-mentioned officers by untiring zeal and energy succeeded in translating the new code, and these officers have 

been ever since reading every message sent over the rebel 

lines. Many of these messages have furnished valuable information to the general commanding the department. 

The following is also from Brown (p. 279): 

About the first of June (1864), Sergt. Colvin was stationed at Fort 

Strong, on Morris Island, with the several codes heretofore used by 

the rebels, for the purpose of reading the enemy's signals if possible. 

For nearly two weeks nothing could be made out of their signals, but 

by persevering he finally succeeded in learning their codes. Messages were read by him from Beach Inlet, Battery Bee, and Fort 

Johnson. Gen. J. G. Foster, who had assumed command of the Department of the South, May 26th, was so much pleased with Sergt. 

Colvin's work, that in a letter addressed to Gen. Halleck, he recommended "that he be rewarded by promotion to Lieutenant in the Signal Corps, or by a brevet or medal of honor." This recommendation 

was subsequently acted upon, but, through congressional and official 

wrangling over appointments in the Corps, he was not commissioned 

until May 13, 1865, his commission dating from Feb. 14, 1865. 

(p. 281): 

During the month, Sergt. Colvin added additional laurels to the fame 

he had earned as a successful interpreter of rebel signals. The enemy 

had adopted a new cipher for the transmission of important messages, 

and the labor of deciphering it devolved upon the sergeant. Continued watchfulness at last secured the desired result, and he was 

again able to translate the important dispatches of the enemy for the 

benefit of our commandants. The information thus gained was frequently of special value in our operations, and the peculiar ability exhibited by the sergeant led Gen. Foster once more to recommend 

his promotion. 

67 co~meEt~flAt 
REF ID:A62856 

HISTORY OF CRYPTOLOGY 

(p. 286): 

About the same time an expedition under Gen. Potter was organized 

to act in conjunction with the navy in the vicinity of Bull's Bay. 

Lieut. Fisher was with this command, and by maintaining communications between the land and naval forces facilitated greatly the 

conjoined action of the command. Meanwhile every means was employed to intercept rebel messages. Sergt. Colvin, assigned to this 

particular duty, read all the messages within sight, and when the 

evacuation of Charleston was determined upon by the enemy, the 

first notification of the fact came in this way before the retreat had 

actually commenced. As a reward for conspicuous services rendered 

in this capacity, Capt. Merrill recommended that the sergeant be allowed a medal, his zeal, energy and labors fully warranting the honor. 

After the occupation of Charleston, communications was established by signals with Fort Strong, on Morris Island, Fort Johnson and 

James Island, Mount Pleasant, and Steynmeyer's Mills. A line was 

also opened with the position occupied by the troops on the south 

side of the Ashley river. 

With regard to Confederate reading of Union visual signals, Brown 

makes the following observations of considerable interest (p. 274): 

The absolute necessity of using a cipher when signalling in the 

presence of the enemy was demonstrated during these autumn 

months by the ease with which the rebels read our messages. This 

led to the issuing of an order that all important messages should be 

sent in cipher. Among the multitude of message,s intercepted by the 

enemy, the following were some of the more important .... 

Brown thereupon cites 25 such messages but he gives no indication 

whatever as to the source from which he obtained these examples or 

how he knew they had been intercepted. They all appear to be 

tactical messages sent by visual signals. 

In many of the cases cited by Brown it is difficult to tell whether 

wig-wag or electric telegraph messages were involved. But in one 

case, (evacuation of Charleston) it is perfectly clear that visual messages were involved, when Brown says that Sgt. Colvin "read all 

the messages within sight." 

Further with regard to rebel cryptanalytic success with Union messages, Brown has this to say (p. 213): 

The reports of Lieut. Frank Markoe, Signal Officer at Charleston, 

show that during the siege thousands of messages were sent from one 

post to another, and from outposts to headquarters, most of which 

could have been sent in no other way, and many were of great importance to the Confederate authorities. 

Lieut. Markoe says that he read nearly every message we sent. 

He was forewarned of our attack on the 18th of July, 1863. He adds 

regretfully, however, that through carelessness of the staff officers at 

headquarters it leaked out that he was reading our messages. Our 

officers then began to use the cipher disk. In August he intercepted 

68 
REF ID:A62856 

W. F. FRIEDMAN CO!l'IFIE>E~HIAL 

the following message: "Send me a copy of rebel code immediately, if 

you have one in your possession". He therefore changed his code . 

. . . A little later our officers used a cipher which Lieut. Markoe says 

he was utterly unable to unravel. 

It is unfortunate that neither Lieutenant Markoe, the Confederate 

cryptanalyst, nor Brown, the Union signalman, tell us what sort of 

cipher this was that couldn't be unravelled. I assume that it was 

the Myer disk used properly, with a key phrase of some length and 

with successive letters, not whole words, being enciphered by successive letters of the key. But this is only an assumption and may be 

entirely erroneous. 

In the foregoing citations of cryptanalytic successes it is significant 

to note that visual messages were intercepted and read by both 

sides; second, that Confederate telegraphic messages protected by 

the Vigenere cipher were read by Union personnel whenever such 

messages were intercepted; and third, that USMTC telegraph messages protected by the route cipher, apparently intercepted occasionally, were never solved. Later I shall make some comments on this 

last statement, but at the moment let us note that technically the 

Vigenere cipher is theoretically much stronger than the route cipher, 

so that we have here an interesting situation, viz, the users of a 

technically inferior cryptosystem were able to read enemy messages 

protected by a technically superior one, but the users of a technically 

superior cryptosystem were not able to read enemy messages protected by a technically inferior one-a curious situation indeed. 

I can hardly close this lecture without citing a couple of messages 

which appear in nearly every account I've seen of the codes and 

ciphers of the Civil War. These are messages which were sent by 

President Lincoln under circumstances in which, allegedly, the usual 

cipher could not be or, at least was not, employed. The first of the 

two was sent on 25 November 1862 from the White House to Major 

General Burnside, Falmouth, Virginia. The circumstances are so 

bizarre that if I merely presented the cipher message to you without 

some background I doubt if you would believe me. And even after 

I've presented the background, I'm sure you won't know what to 

think. I, myself, don't really know whether to take the incident 

seriously or not. Let me quote from an account of it in the book by 

David Homer Bates, one of the first members of the USMTC, in 

his Lincoln in the Telegraph Office (D. Appleton-Century Co., New 

York, 1939, pp. 58-61): 

"During Burnside's Fredericksburg campaign at the end of 1862, 

the War Department operators discovered indications of an interloper on the wire leading to his headquarters at Aquia Creek. These 

indications consisted of an occasional irregular opening and closing 

69 co~menn1AL 
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REF ID:A62856 

HISTORY OF CRYPTOLOGY 

of the circuit and once in a while strange signals, evidently not made 

by our own operators. It is proper to note that the characteristics of 

each Morse operator's sending are just as pronounced and as easily 

recognized as those of ordinary handwriting, so that when a meBSage is 

transmitted over a wire, the identity of the sender may readily be 

known to any other operator within hearing who has ever worked 

with him. A somewhat similar means of personal identification occurs 

every day in the use of the telephone. 

"At the time referred to, therefore, we were certain that our wire 

had been tapped. In some way or other the Confederate operator 

learned that we were aware of his presence, and he then informed 

us that he was from Lee's army and had been on our wire for several 

days, and that, having learned all that he wanted to know, he was 

then about to cut out and run. We goBSiped with him for a while 

and then ceased to hear his signals and believed that he had gone. 

"We had taken measures, however, to discover his whereabouts by 

sending out linemen to patrol the line; but his tracks were well concealed, and it was only after the intruder had left that we found the 

place where our wire had been tapped. He had made the secret connection by means of fine silk-covered magnet wire, in such a manner 

as to conceal the joint almost entirely. Meantime, Burnside's cipheroperator was temporarily absent from his post, and we had recourse 

to a crude plan for concealing the text of telegrams to the Army of the 

Potomac, which we had followed on other somewhat similar ocasions 

when we believed the addressee or operator at the distant point (not 

provided with the cipher-key) was particularly keen and alert. This 

plan consisted primarily of sending the meBSage backward, the individual words being misspelled and otherwise garbled. We had practised on one or two despatches to Burnside before the Confederate 

operator was discovered to be on the wire, and were pleased to get his 

prompt answers, couched also in similar outlandish language, which 

was, however, intelligible to us after a short study of the text in each 

case. Burnside and ourselves soon became quite expert in this homemade cipher game, as we all strove hard to clothe the despatches in 

strange, uncouth garb. 

"In order to deceive the Confederate operator, however, we sent 

to Burnside a number of cipher messages, easy of translation, and 

which contained all sorts of bogus information for the purpose of misleading the enemy. Burnside or his operator at once surmised our 

purpose, and the general thereupon sent us in reply a lot of balderdash 

also calculated to deceive the uninitiated. 

"It was about this time that the following specially important despatch from Lincoln was filed for transmiBSion: 

Executive Mansion, Washington, 

November 25, 1862. 11:30 AM. 

MAJOR-GENERAL BURNSIDE, Falmouth, Virginia: If I should 

be in boat off Aquia Creek at dark to-morrow (Wednesday) evening, 

could you, without inconvenience, meet me and paBB an hour or two 

with me? 

A. Lincoln. 

"Although the Confederate operator had said good-by several days 

COt~FIBEHflAL 70 
REF ID:A62856 

w. F. FRIEDMAN CO~fflBEt~TIAL 

before, we were not sure he had actually left. We therefore put 

Lincoln's telegram in our home-made cipher, so that if the foreign 

operator were still on our wire, the message might not be readily made 

out by the enemy. At the same time extra precautions were taken by 

the Washington authorities to guard against any accident to the 

President while on his visit to Burnside. No record is now found 

of the actual text of this cipher-despatch, as finally prepared for transmission, but going back over it word for word, I believe the following 

is so nearly like it as to be called a true c~py: 

Washington, D. C., November 25, 1862 

BURNSIDE, Falmouth, Virginia: Can Inn Ale me withe 2 oar our 

Ann pas Ann me flesh ends N. V. Corn Inn out with U cud Inn heaven 

day nest Wed roe Moore Tom darkey hat Greek Why Hawk of Abbott Inn B chewed I if. BATES. 

This sort of subterfuge is hardly worthy of becoming embalmed in 

the official records of the war-and apparently it wasn't. But 

several years later, one of identical nature did become so embalmed, 

for the message appears on page 236, Vol. 45, of "Telegrams received 

by the Secretary of War'': 

Hq. Armies of the U.S., City Point, Va., 

8:30 a. m., April 3, 1865 

TINKER, War Department: A. Lincoln its in fume a in hymn to 

start I army treating there possible if of cut too forward pushing is 

He is so all Richmond aunt confide is Andy evacuated Petersburg 

reports Grant morning this Washington Secretary War. BECKWITH. 

Both Plum and Bates cite the foregoing telegram and their comments are interesting if not very illuminating. Plum says merely: 

"By reading the above backward with regard to the phonetics rather 

than the orthography, the meaning will be apparent". Bates says: 

"The probable reason for adopting this crude form was to insure its 

reaching its destination without attracting the special attention of 

watchful operators on the route of the City Point-Washington wire, 

because at that crisis every one was on the Qui vive for news from 

Grant's advancing army, and if the message had been sent in plain 

language, the important information it conveyed might have been 

overheard in its transmission and perhaps would have reached the 

general public in advance of its receipt by the War Department. 

"It is not necessary to give the translation of this cipher-message. 

To use a homely term, 'Any one can read it with his eyes shut.' In 

fact, the easiest way would be for one to shut the eyes and let some 

one else read it backward, not too slowly. The real wording then becomes plain. 

Can you imagine for one moment that a "cryptogram" of such 

simplicity could not be read at sight by any USMTC operator, even 

without having someone read it to him backward? Such a "cryptogram" is hardly worthy of a schoolboy's initial effort at preparing a 

71 co~mBENTIAL 
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REF ID:A62856 

CO~!FIE>E~Hlt\L HISTORY OF CRYPTOLOGY 

secret message. But I assure you that I did not make this story up, 

nor did I compose the cryptogram. 

Ruminating upon what I have shown and told you about the 

cryptosystems used by both sides in the Civil War, do you get the 

feeling, as I do, that the cryptologic achievements of neither side 

can be said to add lustre to undoubtedly great accomplishments on 

the battlefield? Perhaps this is a good place to make an appraisal 

of the cryptologic efficiency of each side., 

First, it is fair to say that we can hardly be impressed with the 

cryptosystems used by either side. The respective Signal Corps at 

first transmitted by visual signals messages wholely in plain language; such messages were often intercepted and read straight-away. 

Then both sides began enciphering such messages, the Signal Corps 

of the Federal Army using a cipher disk invented by the Chief Signal 

Officer, the Signal Corps of the Confederate Army using the Vigenere 

cipher. In both cases the use of cryptography for tactical messages 

was quite inept, although it seems that from time to time the Federal 

signalmen had better success with the Vigenere-enciphered visual 

messages of the Confederate signalmen than the latter had with the 

disk-enciphered messages of the Union signalmen. 

With regard to the cryptosystem used by the Confederate Signal 

Corps, although there may initially have been cases in which monoalphabetic substitution alphabets were used, such alphabets were 

probably drawn up by agreement with the signal officers concerned, 

and changed from time to time. Nowhere have I come across a 

statement that the Myer disk or something similar was used. In 

any event, messages transmitted by visual signals were read from 

time to time by Union signalmen, the record showing a number of 

cases in which the latter "worked out the rebel signal code" -meaning, of course, that the substitution alphabet involved was solved. 

When did the Confederate Signal Corps begin using the Vigenere 

cipher? The answer seems to be quite clear. In a letter dated 6 

June 1888 from General J. H. Alexander (brother of General E. P.) 

to J. Willard Brown9 we find the following statements: 

"At the first inauguration of the Signal Service in the Confederacy, 

I, having received in the first place the primary instruction from my 

brother, Gen. E. P. A., then a colonel on Beauregard's staff near the 

Stone Bridge at Manassas, was assigned the duty of preparing a confidential circular of instruction for the initiation of officers and men, 

in this branch. I did prepare it, in Richmond, in early spring, 1862, 

and surrendered the copy to Hon. James A. Seddon, the then Secretary 

of War at Richmond. It was issued in form of a small pamphlet. 

I had attached a table for compiling cipher dispatches-which was printed 

9 Op. Cit., p. 206. 

COl>IFIE>HHIAL 72 
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REF ID:A62856 

W. F. FRIEDMAN co~mBDHIAL 

with the rest of the matter--and the whole was issued confidentially to the 

officers newly appointed for signal duty. (My emphasis) 

I have italicized the last sentence because I think that the "table 

for compiling ~ipher dispatches" can refer only to the Vigenere square 

table, for that and only that sort of table is even mentioned in accounts of the ciphers used by the Confederacy. One could, of 

course, wish that the writer had given some further details but there 

are none. However, the statement about the table is sufficiently 

explicit to warrant the belief that it was General J. H. Alexander 

who officially introduced the Vigenere square into Confederate 

cryptography, although he may have obtained the idea from his 

brother, since he states that he "received in the first place the primary instruction from my brother". 

In the Federal Signal Corps it is quite possible that the polyalphabetic methods Myer cites in his Manual for using his cipher disk 

(changing the setting with successive words of a message) were used 

in some cases, because there are found in the record several instances 

in which the Confederate signalmen, successful with monoalphabetic 

encipherments, were completely baffled. One is warranted in the 

belief that it was not so much the complexities introduced by using 

a keyword to encipher successive words of the plain text as it was the 

lack of training and experience in cryptanalysis which hampered 

Confederate signalmen who tried to solve such messages. In World 

War I a German Army system of somewhat similar nature was regularly solved by Allied cryptanalysts, but it must be remembered, in 

the first place, that by 1914 the use of radio made it possible to 

intercept volumes of traffic entirely impossible to obtain before the 

advent of radiotelegraphy; and, in the second place, would-be cryptanalysts of both sides in the Civil War had nothing but native wit 

and intelligence to guide them in their work on intercepted messages, 

for there were, so far as the record goes, no training courses in cryptanalysis on either side, though there were courses in cryptography 

and signaling. It would seem to cryptanalysts of 1961, a century 

later, that native wit and intelligence nevertheless should have been 

sufficient to solve practically every message intercepted by either 

side, so simple and inefficient in usage do the cryptosystems employed by both sides appear today. 

No system employed by the Federals, either for tactical messages 

(Signal Corps transmissions) or strategic messages (USM TC transmissions) would long resist solution today, provided, of course, that 

a modicum of traffic were available for study. Although technically 

far less secure in actual practice than properly enciphered Vigenere 

messages, the route ciphers of the USMTC seem to have eluded the 

efforts of inexpert Confederate cryptanalysts. Ex-USMTC operators 

73 CO~fflBDHIAL 
II 

I:, 

l

,,, 

:I 

1:j 

ih 

111.' 

1

1'! 

I;. 

1:1 

I' , ;,j,: 

j,! 

\' 

/, 

REF ID:A62856 

CO~IFl9HHllcL HISTORY OF CRYPTOLOGY 

make the statement that none of their messages was ever solved and 

that the Confederates published intercepted messages in Southern 

newspapers in the hope that somebody would come forward with a 

solution; yet it must be remembered that those operators were 

Northerners who were very naturally interested in making the achievements of the Union operators, both in cryptography and in cryptanalysis, appear more spectacular than they really were. And it is 

probable that they wrote without having made a real effort to ascertain whether the Confederates did have any success. A "real 

effort" would have been a rather imposing undertaking then-as it 

still is, I fear. Now it must be presumed that if Confederate operators had succeeded in solving intercepted traffic of the USMTC they 

would have recorded the facts to their own credit. But in his seven 

volumes on the campaigns of Lee and his lieutenants, Douglas S. 

Freeman does not mention a single instance of interception and 

solution of telegraphic messages of the Union. Perhaps Freeman 

was seeking 1003 confirmation, which is too much to expect in a 

field of such great secrecy. This failure of the Confederate cryptanalysts is the more astonishing when we know that copies of the 

USMTC cipher books were captured and that, therefore, they must 

have become aware of the nature of the route ciphers used by the 

USMTC, unless there was a lack of appreciation of the value of such 

captures and a failure to forward the books to the proper authorities, 

who could hand them over to their experts. In those books the 

USMTC route ciphers would have been seen in their naive simplicity, 

complicated only by the use of "arbitraries" or code equivalents, but 

hardly to the degree where all messages would be impossible to solve. 

It seems to me that there can be only four possible explanations for 

this failure to solve the USMTC route ciphers. Let us examine them 

in turn. 

First, it is possible that there was not enough intercept traffic to 

permit solution. But this is inadequate as an explanation. The 

route cipher is of such simplicity that "depth" is hardly an absolute 

requirement-a single message can be solved, and its intelligibility 

will be determined to a large degree by the number of "arbitraries" 

it contains. Where there are many, only the dim outlines of what 

is being conveyed by the message may become visible; where there 

are few or even none, the meaning of the messages becomes fairly 

evident. But the abundant records, although they contain many 

references to intercepts, fail to disclose even one instance of solution 

of a USMTC message. Thus we are forced to conclude that it was 

not the lack of intercept traffic which accounts for lack of success by 

the Confederates with USMTC messages, but some other factor. 

COll>l~IC)i~lllAb 74 
I I .1 

i 

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REF ID:A62856 

W. F. FRIEDMAN COt~FIE>Et~flAL 

Second, the lack of training in cryptanalysis of Confederate cryptanalysts might have been the reason why Confederate signalmen 

failed to solve the messages. This sounds plausible until we look 

into the matter with a critical spirit. Solution of route ciphers 

requires little training; native wit and intelligence should have been 

sufficient. The degree of intelligence possessed by Confederate 

officers and men was certainly as high as that of their Union counterparts who were up against a technically far superior cryptosystem, 

the Vigenere. We may safely conclude that it was not lack of native 

wit and intelligence that prevented them from solving messages enciphered by the USMTC route ciphers. 

Third, it is possible that Confederate high commanders were not 

interested in communications-intelligence operations or in gathering 

the fruits of such operations. Such an explanation seems on its face 

fatuous and wholely unacceptable. We know of the high estimate 

of value field commanders placed upon the interception and solution 

of tactical messages transmitted by visual signaling; but an appreciation of the extraordinary advantages of learning the contents of 

enemy communications on the strategic level may have been lacking. 

My colleague Mr. Fishel thinks that "intelligence consciousness" 

and "intelligence sophistication" were of a very low order in the 

Union Army, and of a markedly lower order in the Confederate Army. 

But to us, in 1961, to disregard the advantages of a possible reading 

of strategic messages seems almost incredible and I am inclined to 

discount this sort of explanation. 

Fourth, it is possible that Confederate cryptanalysts were far more 

successful in their efforts to solve USMTC transmissions than present 

publicly-available records indicate; that Confederate commanders 

obtained great advantages from their communications-intelligence 

operations; that they fully recognized the supreme necessity of keeping this fact and these advantages secret; and that the Confederate 

States Government adopted and enforced strict communicationsintelligence security regulations, so that the truth concerning these 

matters has not yet emerged. Let it be noted in this connection 

that very little information can be found in the public domain today 

about Allied cryptanalytic successes during World War I; and were 

it not for the very intensive and extensive investigations in the matter of the Japanese attack on Pearl Harbor on 7 December 1941, 

very little, if any, information would be known to the public about 

British and American successes in communications-intelligence 

during World War II. Immediately following the capture of Richmond and before Confederate records could be removed to a safe 

place, a great fire broke out and practically all those records were 

destroyed. It is possible that this is one of the reasons why the 

75 COt~FIE>DHIAL 
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REF ID:A62856 

co~mDHHIAL HISTORY OF CRYPTOLOGY 

records of their communications-intelligence successes have never 

come to light. But it is also possible that Confederate cryptanalysts 

kept their secrets to themselves. We know that the records possessed 

or taken by certain Confederate leaders have been gone over 

with great care and attention, but what happened to those retained 

by other Confederate leaders such as the Secretary of War Seddon, 

or his predecessor Judah P. Benjamin, who later became Secretary of 

State, and others? Here is a fascinating speculation and one which 

might well repay careful, painstaking research in the voluminous 

records of our National Archives. I shall leave the delving into 

those records to some of you young and aspiring professional cryptanalysts who may be interested in undertaking such a piece of research. With this thought I bring this lecture to its close. 

76 
REF ID:A62856 

UNCLASSIFIED 

The Association Factor in Information Retrieval 

BY H. EDMUND STILES 

Unclassified 

This paper describes an all-computer document-retrieval system which 

can find documents related to a request even though they may not be indexed by the exact terms of the request, and can present these documents 

in the order of their relevance to the request. 

All documentalists who are operating large coordinate indexes are 

searching for better ways to exploit this type of information system. 

In our library we have already eliminated the time-consuming job of 

posting document numbers manually by enlisting the aid of a 705 

computer. (The computer periodically prepares revised posting 

cards to replace the outdated ones.) Now we are searching for 

better solutions to our retrieval problems. 

One obvious retrieval problem in any large system is the time required to "coordinate" heavily posted terms. We are convinced we 

must mechanize if we are to allow our collection to grow indefinitely. 

A second problem is the retrieval of so many documents related to 

a single request that the customer finds it difficult to decide which 

document to examine first. Since he has no precise means of determining which document is most closely related to a request, we 

have tried to assist him in using somewhat arbitrary or subjective 

means. The date of the document is sometimes used as a relevance 

criterion, in the hope that the most recent document will be the most 

pertinent, or the name of the author is used, in the hope that the 

work of a known author will answer the request better than that of 

an unknown one. The pitfalls of such criteria are apparent. 

The third, and by far the most serious difficulty in a large system, 

is the problem of choosing terms for search which will turn up all of 

the documents relevant to the request. Our handicap has been that 

we have had to select the precise terms that were originally used to 

index the desired document. Literally hundreds of terms may have 

been used to index documents on the various aspects of a particular 

subject and yet we must grope for just the right set of terms. Just 

as the indexer tried to use language which he hoped would be used 

by future requesters, so the requester must hope to use the same 

This article has been published in the April 1961 issue of The Journal of the 

ACM (Association for Computing Machinery). 

77 UNCLASSIFIED 
I 

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REF ID:A62856 

UNCLASSIFIED INFORMATION RETRIEVAL 

terms that were used by the indexer in processing the required 

documents. 

With our new method we believe we can overcome all three difficulties. First, every step of the process can be performed by existing machines; second, in answer to a given request our machines will 

deliver a list of documents arranged in the approximate order of 

their relevance to the request, and third, we will be able to find these 

documents even though they may not be·indexed by the terms of the 

initial request. 

Our general strategy is to generate by machine an expanded list 

of request terms that will serve as a bigger net to catch documents. 

Once caught we will grade them automatically so that the most important ones will be on top. Our experiment was conducted on an 

existing collection of over 100,000 documents already indexed by the 

Uniterm Coordinate Index System. [1] 

The first step in our procedure is to develop a list of terms arranged according to their degree of association with a given term. 

Frequency alone is not a satisfactory measure of association. For 

example, we counted the number of times various terms had been 

used together with the term "Friction" to index a document and 

found that of the 105 terms used, the most frequent were: 

Theory_ _ _ _ _ _ _ _ _ 7 times 

Film ____________ 6 

CrystaL _ _ _ _ _ _ _ _ 5 

MetaL _ _ _ _ _ _ _ _ _ 5 

Thin ___________ 5 

Transfer ________ 4 

Clutch __________ 3 

})amping ________ 3 

Electrostatic _____ 3 

Although "Metal" and "Clutch" may be significantly associated 

with "Friction", obviously the word "Theory" which is at the top of 

the list has no more relationship to "Friction" than to any other 

word about which there might be a theory. We searched for a formula that would give us a relative frequency-one that would measure the distance from the expected frequency of occurrence assuming no association. After considering several other formulas, including the ones reported by Maron, Kuhns and Ray in their report 

on "Probabilistic Indexing", [2] we decided to use the following: 

( /tN - AB/ - ~) N log10 AB (N _ A) (N _ B) = ASSOCIATION FACTOR, 

UNCLASSIFIED 78 
REF ID:A62856 

H. E. STILES UNCLASSIFIED 

where A is the number of documents indexed by one term; 

B is the number of documents indexed by a second term; 

f is the number of documents indexed by the combination of 

both terms; and 

N is the total number of documents in the collection. 

This formula is a form of the chi square formula using the marginal 

values of the 2 X 2 contingency table and the Yates' correction [3] for 

small samples. If AB > fN the association is negative. Such occurrences must be recognized during the computation process and the 

resultant association factors marked to indicate negative association. 

By applying this formula to each of the 105 terms paired with "Friction" the top of the list became as follows: 

Term 

Wear 

Thin 

Lubrication 

Belt 

f 

2 

5 

2 

1 

A 

4 

49 

9 

2 

B 

25 

25 

25 

25 

Association Factor 

3.35 

3.21 

3.00 

2.70 

"Theory" dropped down to a much more reasonable position, and 

terms such as "Analysis", "Problems" and "Study" were at the 

bottom. "Wear" had risen to the top even though it occurred only 

twice in association with "Friction". Anyone interested in friction 

would probably be interested in the two additional documents indexed by "Wear" and the seven additional dbcuments indexed by 

"Lubrication". 

We tried the same experiment for the term "Exposure" with the 

following results: 

Term f 

Weathering 3 

Plywood 1 

Nylon 2 

Enamel 1 

Microfilm 3 

Preservatives 1 

Lenses 3 

Radiography 1 

Protective 1 

"Exposure" 

A 

3 

1 

12 

2 

52 

3 

77 

4 

12 

B 

29 

29 

29 

29 

29 

29 

29 

29 

29 

Association Factor 

3.86 

2.94 

2.80 

2.63 

2.61 

2.46 

2.44 

2.33 

1.85 

Terms that had association factors of less than one (1.00) were 

discarded. On this basis only a small portion of the terms that had 

been used with "Exposure" (or "Friction") were considered to be 

associated with it. 

79 UNCLASSIFIED 
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UNCLASSIFIED INFORMATION RETRIEVAL 

These term profiles, as we have chosen to call these lists of associated terms, have four important characteristics. First, they are 

derived from the document collection itself rather than from the 

subjective realm of human experience. Therefore only the terms 

that will be useful in finding documents are included and extraneous 

terms are eliminated. Second, they are generated in a statistical 

manner which can be duplicated by an unthinking computer, an encouraging fact considering the future masses of literature to be 

indexed. Third, they reveal the various facets of meaning that the 

term has in our particular collection. The profile for the term "Exposure", for instance, contains terms used when describing "exposure to the elements," "exposure of photographic film," and "exposure to radiation." This characteristic makes explicit the variety of 

meanings that were inherent in the parent term-a fact we will come 

to appreciate when we start combining them. And finally, the profiles derived by this method alone contain terms that are only statistically related and not semantically related to the request term. 

This distinction has been well explained by Maron, Kuhns and 

Ray. [2] 

"Whereas the semantical relationships are based solely on the meanings of the terms and hence independent of the "facts" described by 

those words, the statistical relationships between terms are based solely 

on the relative frequency with which they appear and hence are based 

on the nature of the facts described by the documents. Thus, although 

there is nothing about the meaning of the term 'logic' which implies 

'switching theory', the nature of the facts (viz., that truth-functional 

logic is widely used for the analysis and synthesis of switching circuits) 

'causes' a statistical relationship. Another example might c~ncern 

the terms 'information theory' and 'Shannon' . . . " 

Later we will describe how to derive semantic relationships as well 

as purely statistical ones. 

When we have prepared a term profile for each request term we 

are ready to proceed to the second step, which is to compare the 

profiles of each term of a multiterm request and select those terms 

which appear in all or in a given number of profiles. These selected 

terms are called first generation terms. We are aware of the possibilities in a conventional coordinate indexing system of requesting 

documents that have a logical product, sum, or negation of the request terms. The same flexibility exists when using the association 

factor. If the request is for documents on "American Tractor Tires" 

we would prepare a vocabulary profile for each term and then select 

only those terms which appear in all three profiles. However, if we 

were interested in "American Tractor OR Automobile Tires" we would 

select those terms that appeared in the profiles of "American" and 

"Tires" and either "Tractor" or "Automobile". These first generaUNCLASSIFIED 80 
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tion terms therefore tend to reflect the logic of the request. However we cannot exclude from our first generation terms all the terms 

in the profile of a "not" term because of the danger of also eliminating 

some desirable terms. "Not" terms must be used by themselves to 

eliminate documents that have been indexed by them. If a request 

has only a single term, the terms of its profile are the same as its 

first generation terms. 

The end result of this second step described above, is a list of first 

generation terms which have been used with the original request 

terms to index documents much more frequently than would be expected of terms having no association. Remember also, that these 

first generation terms are only statistically associated with the request 

terms. Synonyms or near synonyms are not likely to be found in 

this list, because documents are not usually indexed by synonymous 

terms. Yet synonyms, near synonyms, generics, specifics, and other 

closely related words would be desirable additions to an expanded 

list of request terms. Our method of generating these constitutes 

our third step. It projects us beyond the purely statistical relationships and into the realm of meaningful associations. This step is to 

treat the first generation terms as request terms and repeat steps 1 

and 2. Since there may be quite a number of first generation terms, 

we need not require that a term appear in all of their profiles, but 

only in approximately one fifth or in some other specified number of 

profiles. The resultant new terms are called second generation terms. 

Among these we find words closely related in meaning to the request 

terms. 

For example, if we were asked for all documents on United States 

wheat exports, the profile of the term "United States" would probably 

not contain the terms "Uncle Sam" or "USA" even if they were 

permissible in our term dictionary, since any given document would 

not be indexed by more than one of the three terms. Since they are 

missing from the "United States" profile, they would not be included 

among the first generation terms. However, when the first generation terms such as "Kansas", "Bushels", "Dollars", "Grain", "Cordell Hull", "Tariff", etc., are treated as request terms, each may 

well have "Uncle Sam" and "USA", as well as "United States" 

among its profiles. Assuming that they will appear in a sufficient 

number of the profiles, they will qualify as second generation terms. 

In our coordinate index we have tried to eliminate all synonyms 

by cross-referencing them to a single term in our term dictionary. 

However, when we requested documents on the "Weatherproofing of 

Fabrics" we derived "Fungus", "Plastic", "Exposure", and "Coating" among the first generation terms, and "Weathering'', "Fungi81 UNCLASSIFIED 
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REF ID:A62856 

UNCLASSIFIED INFORMATION RETRIEVAL 

cidal", and "Preservatives" among the second generation terms. In 

future applications of this system we can expect the second generation terms to include not only synonyms, but also various grammatical forms and even variations in spelling of the request terms. 

We now have an expanded list of request terms. It includes the 

original request terms, the first generation terms and the second generation terms. It is reasonable to assume that these terms do not 

all have the same degree of association with the original request and 

that it would be helpful to determine the degree of association for 

each before proceeding further. 

The fourth step is the preparation of a table of the expanded list, 

in which we would record the association factors of each term to all 

others. We record only those above the established threshold of 1. 

The sum of the association factors for each term, divided by the total 

number of terms in the expanded list, gives us a weight which will 

enable us to arrange the terms according to their probable relevance 

to the request. The expanded list of terms related to the "Weatherproofing of Fabrics" with term weights is as follows: 

Fabrics ____________ 2.67 Deterioration__________ 1.26 

Plastics____________ 2.58 Resistance_____________ 1.25 

Coating ____________ 2.38 Protection _____________ 1.25 

Fungus ____________ 2.28 Agar__________________ 1.23 

Weatherproofing ____ 2.04 Metals________________ 1.21 

Tests______________ 1.90 Plate _________________ 1.17 

Exposure ___________ 1.87 BiphenyL _____________ 1.14 

Compounds________ 1. 76 Dinitrofluorotoluene_ _ _ _ 1.14 

Laminates __________ 1.73 Dinitrobenzene _________ 1.14 

Resins _____________ 1.56 Vinyl_ ________________ 1.14 

Weathering______ _ _ _ 1.52 Preservatives_ _ _ _ _ _ _ _ _ _ 1.09 

Materials __________ 1.43 Elastomers ____________ 1.08 

Glass ______________ 1.42 Molded _______________ 1.06 

Cotton _____________ 1.36 Aluminum _____________ 1.04 

Chemical_ __________ 1.34 Aging _________________ 1.03 

Fungicidal_________ 1.32 Temperature___________ 1.02 

Compressor_ _ _ _ _ _ _ _ 1.27 Fluorine____ _ _ _ _ _ _ _ _ _ _ _ 1.00 

No one word in this list could be substituted for the request, because each has its own variety of meanings and uses, yet it would 

be hard to use a group of them without touching on the subject of 

the reque~t. We now have a powerful tool with which to search for 

documents, for we are not dependent upon the requester and the indexer using the same language. Rather, we have fashioned a request 

language from the consensus of all previous indexing. 

We are now ready for step 5. We compare the expanded list of 

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request terms with the index terms of each document in the collection. 

Whenever the terms match, the weight of the request term is assigned to the corresponding document index term. The sum of these 

weights for each document is called the document relevance number. 

This number should indicate the degree of fit between the request 

and the contents of the document. 

From a request for all documents on the subject of "Thin Films" 

we found the list of document numbers ·indicated in column 1 of 

Table 1. These document numbers are arranged according to their 

document relevance numbers which appear in column 2. We then 

asked a qualified engineer to examine these documents and specify 

which were related to "Thin Films" and which were not. He developed his own rating scale which was as follows: 

Yes-Contains information on "Thin Film". 

M -May be useful background information. 

P -Possibly contains useful background information. 

No -Does not contain information on "Thin Film". 

This engineer was not familiar with our project nor did he have access to any of our results, yet column 3 indicates a remarkably high 

correlation between his evaluation and the document relevance numbers. We then checked back to see how the documents containing 

information on "Thin Film" had been indexed (see col. 4). We 

found that the first five documents on our list had been indexed by 

both "Thin" and "Film". Three more documents had been indexed 

by "Film" alone, and other related terms. Two documents had not 

been indexed by either "Thin" or "Film", but only by a group of 

related terms, yet they contained information on "Thin Films" and 

had a high document relevance number. By using association factors, and a series of statistical steps, easily programmed for a computer, we were thus able to locate documents relevant to a request 

even though the document had not been indexed by the terms used in the 

request. 

The basic 5 steps in our new retrieval method can be summarized 

as follows: 

(1) Prepare a profile for each request term. This profile consists 

of terms that have been used with the request term and have an 

Association Factor greater than 1. 

(2) Compare the profiles of each request term and select those 

terms which appear in all or in a given number of profiles. These 

terms are called first generation terms. 

(3) Treat the first generation terms as request terms and repeat 

steps 1 and 2. The resultant terms which are not already request 

83 UNCLASSIFIED 
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terms or first generation terms are called second generation terms. 

( 4) Make a table of association factors for the expanded list of 

request terms. The sum of the Association Factors for each term is 

called its weight. This weight indicates the degree of association between that term and the complete request. 

(5) Compare the list of expanded request terms with the index 

terms of each document in the collection and add the weights of the 

terms that match. The sum of the weights is called the document 

relevance number. This number is used to present the documents to 

the requester in the order of their probable relevance to the request. 

Thus far, our experiments have been conducted on an existing 

collection of documents already indexed by a manual Uniterm Coordinate Index System. However, we believe that the really significant fact about our discoveries is their potential use in an all-machine 

document storage and retrieval system. Such a system could start 

with automatic encoding of natural language, as described by Luhn 

of IBM, [4] [5] and end with the presentation of abstracts of the desired documents. The results of "auto-encoding", which is a distinctive vocabulary representing the document, might be a more reliable basis for the statistical manipulation of our system than the 

whim of an indexer. For instance, when we searched for documents 

on the weatherproofing of fabrics, we missed one because it had been 

indexed by the terms "Comprehensive", "Study", "Weatherproofing" and no others. Only a search through the one hundred and 

seven documents on weatherproofing would have turned up this 

document. However, if the document had been "auto-encoded", 

the necessary number of distinctive terms would have been ensured. 

The association factor would be useful in selecting incoming documents for dissemination to company engineers. It would form the 

bridge between the language of the engineers requirements and the 

language used in the document. Each requirement would be surrounded with a profile of terms based on those supplied by the engineer and supplemented by those automatically generated from the 

document collection. The index terms assigned to incoming documents would then be compared with these profiles to determine the 

degree to which they fulfilled the requirements. 

Moreover, we should not only be able to provide an engineer with 

incoming material related to his requirements, of which there is 

bound to be too much, but also tell him which of those items contain 

some new information in his field (i. e., new to the document collection). This feat can be accomplished by comparing the profiles of 

the request terms derived from the established document collection 

with the profiles of the request terms derived from a group of inUNCLASSIFIED 84 
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coming documents. Terms appearing in high association with the 

request terms in the new profiles which were not associated in the 

established profiles are indicators of new and distinctive material. 

By treating these new words plus the original request terms as a new 

set of request terms, the documents containing the new and distinctive information can be found. 

Further applications of the association factor are suggesting themselves daily. It is hoped that this presentation will stimulate further 

discussion and experimentation. 

DOCUMENTS RELATED TO "THIN FILM" 

ARRANGED BY DOCUMENT RELEVANCE NUMBERS 

1 i 3 4 

Document Document Degree of Use of Thin 

Relevance and/or Film as Number Numbers Association Index Terms 

S--66,794 24.32 Yes Thin Film 

S--51,212 24.22 Yes Thin Film 

S--51,050 24.22 Yes Thin Film 

S--33,067 24.22 Yes Thin Film 

S--33,068 22.47 Yes Thin Film 

S--95,555 19.87 Yes Film 

S--34,019 15.59 Yes Film 

S--18,958 15.30 p 

S--73,671 14.83 Yes 

S--38,473 12.54 No 

S--37,438 11.81 M 

S--35,837 11.20 M 

S--39,631 10.72 M 

S--35,838 10.14 p 

S--65,855 10.08 M 

S--80,485 10.05 Yes Film 

S--76,529 9.83 Yes 

S--44,571 9.66 M 

S--56,755 9.50 M 

S--42,772 9.38 M 

S--63,862 9.38 No 

S--33,834 9.30 p 

S--33,835 9.30 p 

S--33,832 9.30 p 

S--35,839 9.30 p 

S--80,309 9.18 p 

S--59,129 9.12 p 

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1 2 3 4 

Document Document Degree of Use of Thin 

Relevance and/or Film as Number Numbers Association Index Terms 

S-70,145 8.66 M 

S-59,442 8.03 p 

s-60,834 7.95 M 

S-49,629 7.85 No 

S-71,275 7.27 No 

S-51,499 7.16 p 

S-33,831 7.13 M 

S-31,735 7.13 M 

s-66,513 6.93 p 

S-31,620 6.94 No 

S-31,620 6.94 No 

S-80,360 6.94 No 

s-61,700 6.91 No 

s-44,921 6.40 p 

S-59,130 6.40 p 

S-53,424 6.36 No 

S-78,885 6.03 M 

S-55,371 6.01 No 

S-38,474 5.82 p 

S-80,974 5.33 No 

s-48,093 5.23 No 

S-80,293 5.23 No 

S-55,644 4.65 No 

S-58,247 4.41 p 

s-60,114 4.41 p 

S-45,420 4.41 p 

S-28,975 4.26 No 

S-37,031 2.70 No 

S-71,296 2.70 No 

REFERENCES 

[l] Sanford, Albert and Theriault, Frederic R. "Problems in the Application of 

Uniterm Coordinate Indexing" College and Research Libraries. Vol. 17 

No. 1, January 1956. pp. 19-23. 

[2] Maron, M. E., Kuhns, J. L. and Ray, L. C. "Probabilistic Indexing" RamoWooldridge, Data Systems Project Office, Technical Memorandum No. 3. 

June 1959. 

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[3] Yates, F., "Contingency Tables Involving Small Numbers and the Chi 

Square Test," Supplement to the Journal of the Royal Statistical Society, 1 

(1934), pp. 217-235. 

[4] Luhn, H. P. Potentialities of Auto-Encoding of Scientific Literature, International Business Machines Corporation, Research Center, Research Report 

RC-101, May 15, 1959. 

[5] Luhn, H. P. "Auto-Encoding of Documents for Information Retrieval 

Systems" (In Boaz, Martha, ed. Modern Trends in Documentation. New 

York, Pergamon Press, 1959.) 

87 UNCLASSIFIED 
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TELEPHONE DIRECTORY OF CONTRIBUTORS TO THIS ISSUE 

Author Office Ext:ension 

H. H. Campaigne ____________ REMP ______________________ 7249 

W. F. Friedman* _______________________________________ _ 

W.W. Jacobs _______________ REMP ______________________ 7249 

P. E. Neff ___________________ CSEC _______________________ 60501 

H. E. Stiles _________________ CREF _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7267 

• Special Consultant 

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CGt>JFl9Et>fFIAb 

An Introduction to Cryptology - I 

BY WILLIAM F. FRIEDMAN 

The first of series of lectures prepared by Mr. Friedman for delivery to 1111 aiidience 

assumed to be totally unfamil&aT with the sub1ect. 

The objective of this series of lectμres is to create an awareness of 

the background, development, and manner of employment of a sclence 

that is the basis of a flital militarv of(entnve and defenau1e weapon known 

as CRYPTOLOGY, a word that comes from the Greek kryptos, meaning 

secret or huJden, plus logos, meaning knowledge or learning. Cryptology will 

be specifically defined a little later; at the moment, however, rm sure 

you know that lt has to do with secret co111111unacations. 

Let me say at the outset of these lectures 'that I may from tlme to time 

touch upon ma~rs which are perhaps essentially peripheral or even irrelevant to the niA1n issues. and if a defense is needed for such occaslonal 

browsing along the by-ways of the subject, lt will be that long preoccupaUon wltb any field of knowledge begets a curiosity the satisfaction of which 

is what disUnguishes the dedicated professional from the person who 

merely works just to gain a livelihood ln whatever field he happens to find 

himself a job. That's not much fun, I'm afraid. By the way, a Brltiah 

writer, James Agate, defines aprofesslonalastheman wbo can do his job 

even when be doesn't feel like doing lt; an amateur, as a man who can't 

do his job even when he does feel like doing it. This is pretty tough on the 

gifted amateur and I for one won't go all the way with Agate's definition. 

There are plenty of instances where gifted amateurs have done and discovered things to the chagrin and red-f~edneas of the professionals. 

Coming back now to the main thoroughfare after the foregoing brief 

jaunt along a by-way, I may well begin by telling you that the science of 

cryptology bas not always been regarded as a vital military offensive and 

defensive weapon, or even as a weapon td the first place. Here I am reminded of a story in a very old book on cryptography. The story la probably apocryphal, but it's a bit amusing, and I give it for what it's worth. 

It seems that about two thousand years !l80 there lived a Persian queen 

named Semiramis, who took an active interest in cryptology. She was th 

some respects an extraordinarily unpleasant woman and we learn without 

surprise that she met with an untimely death. She left bebind her instructions that her earthly remains were to be placed in a golden sarcophagus 

within an imposing mausoleum, on the outside ofwbich, on lta front atone 

wall, there was to be graven a message, saying: 

1 C0~4FIBEP~flAL 
REF ID:A62856 

CG~menmAL AN lNTRODUCTION 1'0 CRYPTOLOGY --1 

stay. weary traveller! 

Jf thou art footsore, hungry. or in need of money--

Unlock the riddle of the cipher graven ·below, 

And thou wilt be led to riches beyond all dreams of avarice I 

Below this curious inscription was a. cryptogram, a. jumble of letters 

without meantng or even pronounceabllity. For se~ra.1 hundred yea.rs the 

posslblllty of sudden wealth served as a lure to many experts who tried 

very hard to decipher the cryptogram. They were all without success, 

until one day there 'appeared on the scene a long-haired. be-whiakered, 

and bespectacled savant who, after working at the project for a. considerable length of time, solved the cipher, which gave him detailed 

instructions for finding a secret entry into the tomb. When he got 

inside, he found an instruction to open the sarcophagus, but he had to 

solve several more cryptograms the last one of which may have involved 

flnd1ng the correct combination to a 5-tumbler combination lock --who 

knows? Well, he solved that one too, after a lot of work, and this enabled 

him to open the sarcophagus, inside- which he found a box. Jn the box was 

a message, this time in plain language, and this is what it said: 

O, thou vile and insatiable monster I To disturb these poor honest 

If thou hadst learned something more useful than the art of 

' deciphering, 

Thou wouldst not be footsore, hungry, or in need of money! 

rm frank to confess that manytimeadurlngmy 40-year preoccupation 

with cryptology, and generally near the middle and the end of each month, 

I felt that good old Queen Semir&IDis knew what she wu talking about. 

HOW8'1er, earning money I.a only a put of the recompense for work:lrig in 

the cryptologic field, and I hope that moat of you will find out sooner or 

later what some of these other recompenses are, and what they can mean, 

to you. 

If Queen Semiramis thought there are other thing& to learn that ~ 

more useful than the art of deciphering, I suppose we'd have to agree, 

but we are warranted in saying, at least, that there isn't any question 

about the f.mportance of the role that cryptology plays in modern. times: 

all of us are lnfluenced and affected by It, u I hope to show you in a. few 

minutes. 

I shall begin by 'reading trOm a BOUl'Ce which you'll all recognize--

Ttme , the l.saue of 17 December 1945. -I will preface the reading by remhvltng you that by thl.t date World War D was all over -- or.at least 

V-E and V-J days had been celebrated some months before. Some of you 

may be old enough to remember very clearly the loud clamor on the. part 

of certain voclfel'OU8 members of Congress, who had for years been inCOt~FI BE~HIAL 2 

ai· 

~-
--

REF ID:A62856 

W. F. FRIEDMAN coi-meci-a1AL 

al'Btlng upon learniDg the reasons why we bad been caught by BUl'pl'lse In 

such a disastrous defeat as the Japanese bad Inflicted upon us at Pearl 

Harbor. This clamor bad to be met, for these Congressmen contended 

that the truth could DO longer be hushed up or held back becaue of an 

alleged contlnulng need for military secrecy, as claimed by the Administration and by ma.DJ Democratic senators and representatives. The war 

wu over -- wasn't It? -- Republioan senators and representatives inalated. There bad been lnveatlp.tlona-a half dozen of them-but all except one were To'P Secret. The Republicans wanted-and at lut they got 

what they desired-a grand finale Joint Congressional Jnveatlgatlon which 

would all be completely open to the public. No more secrets! It was spectacular. Not only did the Congressional Inquiry bring Into the open every 

detail and exhibit uncovered by Its own lengthy- hearlnp, but It also diaC?loaed to America and to the whole world everytblng that bad been said 

and shown at all the previous Army and NaTJ lnveatlp.tlona. lllloat of the 

Information that was thus disclosed bad been, and much of It atlll was 

To'P Secret; yet all of these precious secrets became matters of public 

Information as a result of the Congressional lnveaUp.tlon. 

There came a day in the Congreaalonal Hearlnp when the Cllief of 

Staff of the United States Army at the time of the Pearl Harbor Attack. 

5-atai:, General George c. Marshall, wu called to the witness stand. Be 

teatlfled for several long, long da711, eight ofthem In all. Toward the end 

of the second day of bis ordeal he wu questioned about a letter it bad 

been rumored he'd written to Governor Dewey In the Autumn of 1944., 

during the Presidential Campaign. The letter was about codes. With 

frozen face, General Marshall balked at disclosing the whole letter. He 

pleaded moat earnestly with the Committee not to force him to diacloae 

certain of Its contents, but to DO avail. He bad to bow to the will of the 

majority of the Committee. Iahallnowreadfrom Time a bit of Information 

which may be new to many of my listeners, especially to those who were 

toO young In December 1945 to be delving Into periodical literature or to 

be readins any pages of the dally newspaper other than those on which the 

comics appear. 

Said Time, and I quote: 

••u S c1t1zens discovered last week that perhaps their most potent 

secret weapon of World \Yiar II wRB not radar, not the VT fuae, not the 

atom bomb, but a harmleBB httle machine which cryptographer8' had pam• 

stakmgly constructed m a hidden room m Washington With tins mac~1ne, 

built after years of tmd and error, of inference and deduction, cryptographers had duplicated the decoding devices used m Tokyo Testimony 

' before the Pearl Harbor Committee had already shown that the machine, 

known as 'Magic' was 1n use long before December 7, 1941, and had 

given ample wammg of the J aps' sneak attack, 1f only U S. brRSs hats had 

been smart enough to renhze 1t Now, General \'larahall contmued the 

story of 'Magic's' magic 

3 

' ' ': ' 

eot .. FI BEt .. TIAL 
REF ID:A62856 co~menHIAL AN INTRODUCTION TO CRYPTOLOGY - I 

l 'It had enabled a relatively small U.S Force to intercept .a Jap 

invasion fleet, wm a dec1s1ve victory 1n the Rattle of the Coral Sea, thus 

saving Australia and New Zealand. • · 

3. 'It bad directed U.S. anbmannea nnemngly to the sea lanes where 

Jap1111ese convoys would be pus1ng. 

2. 'It had given the U S full advance 1nformat1on on the sue of the Jap 

forces advancing on \lhdway, enabled our Navy to concentrate ships 

which otherw111e might have been 3,000 miles away, thus set up an ambush 

which proved to be the tum1ng-pomt victory of the Pac1f1c war 

4. 'By decoding measages from Japan's Ambaaaador Oshima 10 Berhn, 

often reporting 1nterv1ewe with Hnler, 1t had given our forces 10valuable 

1nfo~at1on on German war plan~'.'·' 

Time goes on to give more details of that story, to which I may later return but I can't leave this citation of what cryptology did toward our winning of World War II without telling you that the account given by Time of 

the achievements of Maf11.c makes it appear that all the secret intelligence 

galJied from our reading Japanese messages wu obtained by usiJ!.g that 

"harmless little machine" which Time said was used ln Tokyo by the 

Japanese Foreign Office. I must correct-that error by explaining first 

that Magic was not the name of the machine but a term used to describe 

the intelligence material to which the machine, among other sources, 

contributes and then by telling you that the secret information we obtained that ~y bad little to do with those portions of the Magic material 

which enabled our Navy to win such spectacular battles as-tbo&e of the 

Coral Sea and Midway, and to waylay Japanese convoys. The naval parts 

of Maf11.c were nearly all obtained from Japanese naval messages by our 

own Tery ingenious U.S. Navy cryptanalyst&. At that time, I may tell those 

of you wbo are new, the Army and Navy bad separate but cooperating 

cryptologic agencies and activities; the United States Air Force was not yet 

ln existence as an autonomous 1.nd separate component of the Armed 

Forces, and work on Japanese, German, and Italian air-force communications was done by Armycryptanalysts, ad.mirahlyustatedby personnel of 

what wu then known as the Army Air Corps. 

It is hardly necessary to tell you bow carefully the Magic of World 

War Il was guarded before, during, and after the war until the Congressional Inqulrybrougbtmostofitoutintbe open. Some remaining parts of it 

are still very carefully guarded. Even the fact of the existence of Magic 

waa known to only a very few persons at the time of P,earl Harbor -- and 

that ta an important element ln any attempt to explain why we were caught 

by aurpriae by the Japanese at Pearl Harbor ln a devastating attack that 

crippled our Navy for many months. Let me read a bit from page 261 of 

the Repprt of the Majority of the Joint Congressional Investigation of 

the attack: 

eet~!=l 8Et~f1AL 4 
REF ID:A62856 

W F FIDED'WAN co~~FI BEt~fli'\t 

"The Magic 1ntelhgence was pre-emmently important and the necessity for keeping it confidential cannot be overestimated However, so 

closely held and top secret was this intelligence that it appears that 

the fact that the Japanese codes had been broken was regarded as of 

more importance than the information obta1ned from decoded traffic." 

Time says, in connection with this phase of the story of Magic during 

World War Il 

"So priceless a possession was Magic that the U S high command 

hved In constant fear that the Japs would disco~er the secret, change 

their code machinery, force U S cryptographers to start all over again " 

Now I don't want to over-empbasizetheimportanceof communications 

intelligence in World War n. but I think it warranted to read a bit more of 

what is said about its importance in the Report of the Majority. The 

following is from p. 232· 

all witnesses famihar with Magic material throughoot the war 

have test1f1ed that 1t Lontr1buted enormoosly to the defeat of the enemy, 

greatly shortened the war, and saved many •thousands of lives." 

General Chamberlin, who was General MacArthur's operations offwer, 

or G-3, throughout the war in the Pacific, has written: "The information 

G-2, that is, the intelligence staff, gave me in the Pacific Theater alone 

saved us many thousands of lives and shortened. the war by no less than 

two years." We can't put a dollars-and.:.cents value on what our possession of co-.i1N r meant in the way of saving hves, but we can make a 

dollars-and-cents estimate of what commumcatlons lntelhgence meant by 

shortemng the war by two years, and the result of that estimate ls that it 

appears that $1.00 spent for that, sort of intelligence was worth $1,000 

spent for other military actlVltles and materials 

In short, when our commanders bad that land of intelligence in World 

War Il they were able toputwhatsmall forces they had at the right place, 

at the right time. But when they didn't have it--and this happened, too, --

their forces often took a beating. Later on we'll note instances of each 

type. 

I hope I've not tried your patience by such a lengthy preface to the 

real substance of this series of lectures, let's get down to brass tacks. 

For those of you who come to the subject of cryptology for the first time, 

a few defimtions will be useful, in order that what I shall be talking about 

may be understood without question. Agreement on basic terminology is 

always desirable in tackling any new subject. In giving you the definitions there may be a bit of repetition because we shall be looking at the 

same terms from somewhat different angles. 

5 (;9~ffl0EtHIA:L 
REF ID:A62856 

CONFl9EtHIAL AN l~TRODUCTIOl'i TO CRYPTOLOGY - l 

First, then, what is cryptology? Briefly, we may define it as the A 

doctrine, theory, or branch of knowledge which treats of hidden, dis- W 

guised, or secret communications. You won't find the word in a small 

dictionary. Even Webster's Unabridged defines it merely as "secret or 

enigmatical language'', and in its ••Addenda Section'', which presumably 

contains new or recently-coined words, it is defined merely as "the 

study of cryptography". Neither of these definitions is broad or specific 

enough for those who are going to delve somewhat deeply into this science. 

Cryptology bas two main branches; the first is cryptography, or, very 

briefly, the science of preparing secret communications, and the second 

is cryptanalysis, or the s01ence of solving secret communications. Let's 

take up cryptography first, because as a procedure it logically precedes 

cryptanalysis: before solving anything there must be something to solve. 

Cryptography is that branch of cryptology which deals with the various 

means, methods, devices, and machines for converting messages in 

ordinary, or what we call plain language, into secret language, or what we 

call cryptograms. Here's a picture of one of the most famous cryptograms in history. It was the solution of this cryptogram which resulted in 

bringing America into World War I on the side of the Allies on 6 April 

.... * .............. ..._ .... _ .... -..C, ..... _....,,.__ I 

GD•Ah Lr.GA•lCil \::/ /. 

1r:xzcc, c1•v 

UC 13042 nee er.c1 115 3528 418 17214 0.11 11310 

UU4"" 18222 21.,f'C 1)247 11';18 23117? 13!!05 H94 HNO 

dCS-2 59::. 11311 h39.i 103"11 03G2 21290 5181 311195 

3.- 1""5C4 t12•n 182"• :18101 0:!1? C228 11e9' 4473 

.. nt1• 2£2('() 1c.4c~ 21589 e7&93 S1

1B9 1:1918 A9118 12137 

1:!33 47>:f> H5e 59~ 5 17199 13851 4458 17149 IHH ll70ll 

1385'1 :224 f'Ci29 1'1991 7382 158~" e?893 1'218 *" 1"" .... """L"' 5t11""(' 54!:.1 ie c~ 11ii21 ? 12801 17118 

1C('1 ""3"'tii 71H' 2"('38 tB2t2 P719 1433'1 '19021. 

.... " { 

::,u&,f 

19HC 2l2f'C 

ac-.rr 

59C• 

218(,4 

1'534"1 

4""'l? 

204!<0 

.. ,. 224C: 

_, 21181111 

1S7H 

nn 

IOtll? 

- ~·· "'::""· '85 'r.22112 13~ 2204.Q 13339 11181 22111 

1C'43'J 14tll4 ,,.,. t'l92 8794 7e32 '73~T 

-·- 11.87 

211 0 212'72 ~.e ~!>&> ~ .. 6f'4 158?4 18501 ~ 

218• 53-~ ""\381 98C91 Je127 1:54K 9350 92211 

--Ulll 

~lH 2831 1792&"1 1134, 1.'142 'l1:i::G4 .... ??el 

10482 117511• 35Cl9 se•r BEPMl'llltl'I' • 

-- Jo'1g 1 - The Z1mmennan Telegram 

cor-1i;1ei;:r-111i°'iL 6 
REF ID:A62856 

W F FRJEDMAl\ COP.JFl9HHIAL 

1917, justaboutsixweeksafteritwassolved. I'll tell you about it later ln 

tlus series. 

Cryptography also includes the business of reconverting the cryptograms into their original plain-language form, by a direct reversal of the 

steps followed in the original transformation. This imphes that the 

persons involved in both of these bits of business, those at the enciphering 

and sending end, and those at the receiving and deciphering end, have 

an understanding as to what procedures, devices, and so on, will be used 

and exactly how--down to the very last detail. The what and the how of the 

business constitutes what is generally referred to as the key • The key may 

consist of a set of rules, alphabets, procedures, and so on; it may also 

consist of an ordinary book which is used as a source of keys; or it may 

be a specialized book, called a code book That cryptogram I just showed 

you was made by using a book--a German codebook. 

To encrypt. ls to convert or transform a plain-text message into a 

cryptogram by following certain rules, steps, or processes constituting the 

key or keys and agreed upon in advance by the correspondents, or furnished them by higher authority. 

To de crypt ls to reconvert or to transform a cryptogram into the 

original equivalent plain-text message by a direct reversal of the 

encrypting process that ls, by applyingtothe cryptogram the key or keys, 

usually in a reverse order, employed in producing it. 

A person who encrypts and decrypts messages by having in his possession the necessary keys, is called a cryptographer, or a cryptographic clerk. 

Encrypting and decrypting are accomplished by means collectively 

designated as codes and ciphers. Such means are used for either or both of 

two purposes (1) secrecy, and (2) economy. Secrecy usually is far more 

important in diplomatic and military cryptography than economy, but it 

is possible to combine secrecy and economy in a single system. Persons 

technically unacquainted with cryptology often talk about "cipher codes", 

a term which I suppose came lntouseto differentiate the term "code" as 

used in cryptology from the same term as used in other connotations, as, 

for example, the Napoleonic Code, a traffic code, a building code, a code 

of ethics, and so on. Now, in cryptology, there is no such thing as a 

"cipher code". There are codes and there are ciphers, and we might as 

well learn right off the differences between them, so that we get them 

straightened out in our minds before proceeding further. 

In ciphers, or in cipher systems, cryptograms are produced by applying the cryptographic treatment to individual letters of the plain-text 

messages, whereas, in codes, or in code systems, cryptograms are 

produced by applying the cryptographic treatment generally to entire 

words, phrases, and sentences of the plaJ.n-text messages. More specialized meanings of the terms will be explained in detail later, but in a 

moment I'llshowyouanexampleofacryptogram mcipher and one incode. 

1 

7 -... COP.JFl9nHIAL 
REF ID:A62856 

COt<tFl6Et<tllAL AN I"ITRODUCTION TO CRYPTOLOGY - l 

A cryptogram produced. by means of a cipher sys~m is said to be in A 

cipher and 1s called a cipher message, or sometimes, simply af'ipher The W 

act or operation of encrypting a cipher tnessage is called et~r iphermg, and 

the enciphered. version of the plain text, as well as the act or process itself, is often referred to as the encipherment. A cryptographic clerk who 

performs the process serves as an encipfierer. The correspond10g terms 

applicable to decrypting cipher messages are deciphermg, decipherment, 

dt> ciphere r. 

A cryptogram produced. by means of a code system is said to be in 

code, and is called a code message The text of the cryptogram is referred. 

to as code tezt This act or operation of encrypting is called encoding, and 

the encoded version of the plain text, as well as the act or process itself, 

is referred. to as the encodement The clerk who performs the process 

serves as an encoder The corresponding terms applicable to the decrypting 

of code messages are decoding, decodement, and decoder. A clerk who encodes and decodes messages by having m his possession the pertinent 

code books is called a code clerk. ~ 

Technically, there are only two distinctly chfferent types of treatment 

which may be applied to written plain text to convert it into a cipher, 

yielding two different classes of ciphers. In the first, called transposition, 

the letters of the plain text retain their original identities and merely 

undergo some change in the relative positions, with the result that the e 

original text becomes unintelligible. Here's an authentic example of a 

transposition cipher, I call it authentic because it was sent to President 

• 

CONFIBEUTIAL 8 
REF ID:A62856 

W. F. FRIEDMAN COl'llPICU!l'llTIAL 

Roosevelt and the Secret Service llSked. me to decipher lt. Imagine my 

chagrin when I bad to report that lt sa:ya "Did JOU ever bite a lemon?" 

In the second, called au6atitvtion, the letters of the plain text retain their 

original relative positions, but are replaced. byotbar letters with dlffe1'8Dt 

BOUDd values, or by symbols of some sort, so that the original text 

becomes unintelligible. 

Nobody will quarrel with ;you very bard lf JOU wish to say that a code 

s:yatem ls nothing but a speclallzed 

form of substltutlon: but It's best 

to use the word •'code'' when a code 

RUMRICB SPY CASE IGUENTHER GUSTAVE llUMlllCH IT -AL) 

PHOTOGRAPHIC COP'I OF THE CIPHER WITH THE GERMAN AND ENGLISH DECIPHERING INTERLINED 

-/- o/.J.-t -- of'>-"/ T"~·H o-1, ,...,,.,_ 

LIEBE JENNI I NA.CH 11181 11000 

DEAR JENNIE PL£ASE 80 TD MISS ll008 

/-•O ..L-••'( J~ llf'>~J''''I- ,,_,,,.,/:: 

GE H llTTE AM AIFAHRTSTAG z•1BCHEN 

ON THE OAr OF DE,,.RTUll£ BET•EEN 

J-rn;, 'f11t1t _,, "'!I- ,,T~".J. -.- .. -10 

:S- 5 UHR DANt.I IST DER DOK TOR NICHT •-5 O'CLOCK TH£N THE OOOTOll WILL NOT BE 

-?.- "'> ., ... IJ v;'tf 'ff.I,. ¥~-11., r--1''"' DA DER SOLL VON DER SACHE NI CHTS 

THEllE HE IS NOT 1V ltNOrl AN'ITH/118. AaOUT 7'S 

r-n-1r L-1-r~.>' ~---....... 

WISIEN DEIN KARL 

llATTEll l'OllW ltAll&. 

~~ ~ .: 

Fl1. 3 

... .,. ... , .... ,. .. ,""' , . , *"'"""' .. ,, ...... ....... , ... ~· ... ' .... ,,. .......... ~ 

..... ,, .... ,,... ,_,.II~.,,,, 

the cipher text or enclpherment. 

book ls Involved, and to use "subslltutlon cipher'' when a literal system of substltutlon ls ued. 

B ls possible to encrypt a message by a substitution method and 

then to apply a transposition method 

to the substitution text, or vice 

versa. Comblned trasposltlon-substltutlon ciphers do not form a tblrd 

class of ciphers; they are only occasionally encountered ln mllltary 

cryptography. Applying a cipher to 

code groups ls a very frequently 

used procedure and we'll see cases 

of that too. 

Here's an Nr!!mple of a substitution cipher, and a very simple one • 

It wu found on a German spy ln 

World War D. Here's the cipher 

alphabet; here's the plain text which 

happened to be ln German; and here's 

Now for an example of a cryptogram ln code. On the following page 

ls a plain-text message ln the handwriting of President Wilson, to bis 

special emissary ln London, Colonel Bouse. Also contained on the 

next page ls the ct yptogram after the plain text wu encoded by Mrs. 

-Wllson. The President then himself typed out the flnal message on bis 

own typewriter, for transmission by the Department of State. It would 

appear that President Wilson lacked confldsnce ln the security of the 

Department of State's methods--and maybe with good reason, as may be 

seen ln the following extract from a letter dated 14 September 1914: 

from the President to Ambassador Page ln London: 11We have for some 

tlme been trying to trace. the leaks, for they have occurred frequently, 

and we are now convinced that our code ls ln possession of persons at 

9 co~~FI 9ENf IAL 
REF ID:A62856 

CONFIBEt~flAL Al'I INTRODUCTION TO CRYPTOLOGY -I 

J,,,.,~ AA fS.,.,_._I ~ t:nil/C 

I /--, ~ ~ ,1'-u_et;" 

-:;~ .!; .r--rC)- - .t;''t'i";:) £,.,.. e.r- ~ r- 11:'~-"'­

~~1'-4-

4..a r-..; .4-7--1-

~ --r--- --u- ~ ? ..,1r. 

o1- ~ ./.._../-- v .,e,.; ./ J'~ et::. ~f- --fo-... /.;;;.,~,~---

.#:" 

Fig 4 

3U,a'il'-333?1 - '37~oa­

"1"fo<. -3:/.0'fo-22.Nf.-l"J.9&,? 

I~ 7.at. - Z••itl(-,S"o?~-4,.. .... -7.tG-lo 

.1101r11 ~- - 1a& / 3 -r11o'"r-(l:!IJ3' -1~?1'­

'tl.! ~-a. -.l!a.&¥.3 -G.ro&a ~!t/_7-/)'¥02 

"'' s-, -z .. ,,.t,. -3,r&a-''f"V~,733 

~ '111(:.1.-17~ ra- '''3,1-fi'l11.·7-la7s-1 

~h ~ &-/ 7~·0:.-3'''"·.Jill/20 -94'30 

:J:u,G.:z-170<. -1,J/3.l/-4N~& -Jt1IO It 

1/1/'l'iffiintermediary points. We are going to take thoroughgomg measures.'' A 

Perhaps one of the measures was that the President got himself a code of • 

his own. I must follow this up some day. 

A cipher device is a relatively simple mechanical contrivance for 

encipherment and decipherment, usually ''hand-operated'', or manipulated 

by the fingers, as for example, a device with concentric rings of alphabets, 

manually powered. On the next pageisanexample-- a cipher device with 

such rings. I'll tell you about it later. A cipher machine is a relatively 

complex apparatus or mechanism for encipherment and decipherment, 

usually equipped with a typewriter keyboard and generally requiring an 

external power source. Modern cryptology, following the trend in mechanization and automation in other fields, now deals largely with cipher 

machines. some highly complicated. Also pictured on next page is a 

modern cipher machine with keyboard and printing mechanism. 

One of the expressions which uniformed laymen use, but which you 

must never use, is "the German code", or "the Japanese code", or 

"the Navy cipher", and the like. When you hear this sort of expression 

you may put the speaker down at once as a novice. There are hterally 

hundredEI of different codes and ciphers in simultaneous use by every 

large and important government or service, each suited to a special 

purpose, or where there is a multiplicity of systems of the same general A 

nature, the object is to prevent a great deal of traffic being encrypted. in W' 

the same key, thus overloading the system and making it vulnerable to 

C9~ffl9EtHIAL 10 
REF ID:A62856 

W F FRIED\! o\N COl>IFl9EPHIAL 

FJg, 7 • TSEC/KL·7 CJpher Wachane (U S.) 

11 co~~FIBEPHIAL 
REF ID:A62856 

co~menmAL All{ I'l"TRODUCTIOI\" TO CRYPTOLOGY- I 

attack by methods and procedures to be mentioned 10 broad terms a 

in a few moments. W 

The need for secrecy in the conduct of important affairs has been 

recognized from time immemorial. In the case of diplomacy and organized 

warfare this need is especially important in regard to communications. 

However, when such communications aretransmittedbyelectricalmeans.-

they can be heard or, as we say, intercepted, and copied by unauthorized 

persons, usually referred to collectively as the enemy. The protection 

resulting from all measures designed to denytothe enemy information of 

value which may be derived from the interception and study of such 

communications is called communication security, or, for short, CO\ISEC. 

In theory, any cryptosystem except one, to be discussed in due time, 

can be attacked and "broken", i.e., solved, if enough time, labor, and 

skill are devoted to it. and if the volume of traffic in that system is 

large enough. Tins can be done even if the general system and the 

specific key are unlmown at the start. You will remember that I prefaced 

my statement that any cryptosystem can be solved by saying "in theory, .. 

because in military operations theoretical rules usually give way to practical considerations. 

That branch of cryptology which deals with the principles, methods, 

and means employed in the solution or analysis of cryptosystems is called 

cryptanalytics. The steps and operations performed in applying the principles e 

of cryptanalytics constitute cryptanalysis To cryptanalyae a cryptogram is to 

solve it by cryptanalysis. A person skilled in the art of cryptanalysis is 

called a cryptanalyst, and a clerk who assists in such work is called a 

cryptanalytic clerk. 

Information derived from the organized interception, study, and 

analysis of the enemy's commurucations is called communication intelligence, 

or, .for short, cm.UNT Let us take careful note that C0\111\1 and COMSFC' 

deal with commurucations. Although no phenomenon is more familiar to 

us than that of commurucation, the fact of the matter is that this magic 

word means many things to many people. A defimtion of communication 

that is broad enough for our purposes would be that communication deals 

with intelligent messages exchangedbetweenintelligentbe10gs. This implies 

that human beings, and human operators are involved in the preparation, 

encryption, transmission, reception, decryption, and recording of messages which at some stage or stages are in written form and in some 

stage or stages are in electrical form as signals of one sort or another 

But in recent years there have come into prominence and importance 

electrical signals which are not of the sort I've just mdicated. They do 

not carry "messages" 1n the usual sense of the word, they do not convey 

from one human bemg to another an 10telligible sequence of worps and an A 

intelligible sense. I refer here to electrical or electronic signals such W 

as. are employed in homing or directional beacons, in radar, in telecet<lfl O!!l"iTl:A:L 12 
REF ID:A62856 

W F. FRIED\IA.lll" co~~FIBEl'nlAL 

e metering or i·ecording data of an electrical or electronic nature at a 

distance, and so on. Information obtained from a study of enemy electronic 

emissions of these sorts is called electronic inteHt.gence,or, for short, 

Jo~Lll\'I' The particular or specialized study of enemy radar signals is 

called RADIST All these, COM~'I'. ELINT, RADINT comprise SIGINT, that is, 

11ignal intelligence. Cryptology is the science which ls concerned with all 

these branches of secret signalling. 

In this series of lectures we shall be concerned only with CO\fSEC and 

COMINT, leaving for others and for other times the subjects of ELINT, 

llADThT, and so on. This means that weshalldeal with communications or 

messages 

Communication may be conducted by any means susceptible of ultimate 

interpretation by one of the five senses, but those most commonly used 

are seeing and bearing. Aside from the use of simple visual and auditory 

signals for communication over relatively short distances, the usual 

method of communication between or among individuals separated from 

another by relatively long distances involves, atone stage or another, the 

act of writing or of spealang over a telephone. 

Privacy or secrecy in communication by telephone can be obtained by 

using equipment which affects the electrical currents involved in telephony, e so that the conversations can be understood only by persons provided 

with suitableeqwpmentprC?J>erlyarrangedforthepurpose. The same thing 

is true in the case of facsimile transmission (i.e., the electrical transmission of ordinary writing, pictures, drawings, maps). Eventod.aythere 

are already simple forms of enciphered television transmissions. Enciphered facsmrlle ls called CIFAX, enciphered telephony, CIPIIONY, and 

enciphered television, CIVJ.SIO!lt • However, these lectures will not deal 

with these electrically and cryptanalytically more complex forms of 

cryptology We shall stick to enciphered or encrypted wribng--wluch will 

be bard enough for most of us. 

Writing may be either visible or invisible. In the former, the characters are inscribed with ordinary writmgmaterlals and can be seen with 

the naked eye: in the latter, the characters are inscribed by means or 

methods winch make the writing invisible to the naked eye. Invisible 

writing can be prepared with cert8.ln chemicals called sympathetic or 

secret inks, and in order to "develop" such writing, that ls, make it 

visible, special processes must usually be applied. Shown on the next 

page is an interesting example--the developed secret-ink message that 

figured in an $80,000,000 suit won by two American firms against the 

German Government after World War I sabotage was proved. There are 

A also methods of producing writing which is invisible to the naked eye 

W because the characters are of microscopic size, thus requiring special 

microscopic and photographic apparatus to enlarge such writing enough to 

13 co~mBEt<ITIAL 
I 

REF ID:A62856 

COt4FIBEtHIAL AN INTRODUCTION TO CRYP!fOLOGY - I 

The Yukon Trail THE Burr; 

I 

.______ ______ _____.\. 

Fig. 8 

CO~IFIBEtHIAL 14 
REF ID:A62856 

W. F. FRIEDMAN 

·make lt visible to the naked eye. 

-·}£._--':.;:;..-.... ••• ,._:~ .... ~.:-.: ... z..~' • .;o Here's an eumple--acodemessap .... "'",._,..,........,..., .. ,....,.,,,,. -.--.. --,..-.. ,,. ... "-:.-~-:I not h 1 the ·::=..:::~:~~~·· .. .,..1 --"'"':--·"' ... -.:..:. .... ., ... IW"C,-~ n a apace muc arpr than .............. ,... !""" ...... .-c ... _ .......... "',. .......... Ml .... .,.,. 

........ -:::'"'-~""" ..... _, __ , __ · ·' ··"bead of a pin. A slmple deflnltlonof .. llr .. ___ ....... :::::... :;! - .......... - .................... - ......... _.:i: 

::::;::: ...... :·--..-Z- ... ~:;=-4;;:::;;.: ~~~::? secret writing would be to say that ............... J.._,_.,.,,,...""' ........... _,_ .:.::::.:...:.,..:: .. ·.,., "'·~ - ~--.......... ,... ... lt comprises lnvlslble writing and 

"';-..... 'I;.=- .... 11-l ..... ~ .. - ...: _:;:~ ... ~:::.~;:;:-

' ;:;:~ "" ;--• _ "':::·.: - _ _._ • .i.-... -1 .. -· ... -·--·. wdnteWglble visible writing • .Jo ... - _,.._ .. ,. ... ., ... _,... ..... _ .... 

~.:~::..~ .:::..~· ;,~ . .-.:-_ ~. -M----~"' ------··• There ls one additional piece of A ..... -.......... ~ • ... - ., .. _ ._,..._ '"°.:.H .. • ~,.rf 

.... _,..,. ..... .;-.. __ ,: .. · -:-:""":;!-~·-· .... ,.... •'basic information which It is 'wise -...--::-::=.~*:..:: ..... I.. -"' ... Wt;. ..... ;; ............ .:. .. t .... ~ 

?t;; ....... ~_.....,...: :.~:":..::::;:;:~":::.::to call to your attention before we ----~-_ ...................... - ... "' ... _ ..... .,..._ .... ..., .. ,., ,. ..... ... :::::--::~ .... ~..... '"'·-·-·· ..... -..... , .. proceed much further, and I'll begin 1--·-=-·~-_....~:~, :::;::.:.:::::·~-' --.... --......... .,, - ... _..,__. .... ~, by stating that the greatest and the ~-~·~-~~~-~-~~~ -•-w~"-...-~.-p-......... - =:.::,::~::::-:::: · ~:::;.-:-=:-:!'?;::: moat powerful Instrument or weapon 

"':::-S..!;~::::!::-::::= :::;;=::=.::::=_' ever forpd. and 1mprovecl by man ID ...... _ .... ,..,..,,. .. .,..... .s!', .... ___ .. .,._.,. .... ~ 

:.::-~-:-"!:'='.:"':- -, ~::;~;:::::.":~:::?:::~. 11ds long atrugle for emancipation 

·::;·.::;:~ !:.':=;-: • :

1 

::::::;:~-:::=:: from utter depelldence upon bla own ......... __ --=-· ......... ..... .. - ........ _ ............. - :~: :_:~z.~':._"._~., _·.- · ""-·:_ -~ . .:. envlronment Is the weapon of lit-

" . - .•••• - ~ • - ,, t of .... i.... and .,.,,.....,_,,,...,. __ ...,..,._ .... -... .__ .. __ •"""._l9i!:W 9 - .J.,,.. _,..._.,_.,. ........ _ .. Lr .. ..... -....... ,. ... ,. __ .... __ :::::::::~.:.;c:i:: 

.... ,., ... ""' ... --.. --wo.,...,. ....... -............... ., ....... ., ......... 

e .... -............ _..,r,....,._ .. _ ........ _ ......... ,.""',. __ ,.. :.==~::.:.::::::~.:: ... ~ ...... _ .. _ ... __ ..... ._ ........ ~ ... -......... -"\ ............ .. _ ......... ~ ... ,.1111 .............. i.o .. .... _ ... ,-.... •1- ... _ .. __ "' .... """' .. _____ .. 

... ;.. 

--.. .... -.............. ~--- .. ............. ..,-.......... _ ........ ..... -... ,-... ----.. --

'·':.::::--~- -·-- - eracy--a mas ery re,...... ~-- · " ;- :- -:: ~ wrltlng; and the most imporbm.t - r ... .. .... ..... .., -·-- .J .._ 

.... -· .......... _ ..... ~ 

.... -... -............ ... :~:;:~::::::=~-- ---~ """' ..... _,,. '.,,.,._ ... - ~ -:,.,.: : ::..-:;:::.:~:::::- ... 1a.1.,. ... .,.,_ ..... __ ..,.._, -

__ .............. _ .... ..,..;.. .. -::... M I .... ¥1"''" __ .._..., ___ W:-9 

_ ............. -,,_ ........... ... ..... -.... __ .. _ .... - ...:-. ... ,,.._,"' ......... ,. ... .,_,J ..- ...... ~ ......... _ .. ___ ••-'-.. 

<; .. ~ ............ - ......... .,.11" ... ..... •-r¥• -..,-w.... ... .. ,,. .. -..... ------.ii:.--\ --~--.,. ....................... . - .. --.. ~-- ••••PJ,••• .,..... .. - ......... ---............. 1 

...... ~-~-·-••w•~~-~ 

........ ~~· ..... ~~·-·~· !-....... .... ... 1- ..... 1-..i: ... 1 .:.:: ......... .::.,"!:,,"!. ....... __ _. ......... -........ ., ... 

:llmm.tlon, the one that made the 

weapon of literacy ,,acucal, was the 

Invention of the al71Aa1'et It ls therefore a rather strlldng anomaly that 

we should now come to the study 

of another weapon--& counter-weapon to the weapon o.f literacy--the 

weapOD. of HCNC'V, the basic intent af 

wblch is to thwart the weapon that 

man struggled so long to forge • 

·Secrecy ls applied to make wrltlng 

... .. _ .............. __ )"'I_--.: 

.... 'W .,......_ ___ ·--· "" -....... _ ... -..... .. 

... -: ... .. ~ ..... ... 

,. ~ i:. ... _ ............ , 

- ....... - .. .:;_ 

......... _"JO _._ ........... ' . ,,. more dlfflcult and the reading of 

... - '"'''"""·"'""~ ,..._,\ .. .,.. .. ,. _, ... :" ... 111• ... 1 .. 11111'•"'·"'' -... ...:.. - - ~· -J ol. the writing very dlfflcult, If 

• · -~ ••• not Impossible. ' F11. 9 Perhaps this is a good plaqe to 

do a bit of theorlzlDg about this matter of secrecy and what it Implies. 

Every person who enolpbers a piece of wrltli:lg, a message, or a text 

of any kind, for the purpose of hiding something or of keeping something 

secret, does so with the idea that some other person, removed from him 

ln distance, or time, or both, ls Intended to decipher the writing ormeasap and thus uncover the secret which was so hidden. A person 

may possess a certain piece of knowledge which he does not wish to 

a forget, but which he' ls nevertheless unwllllng to commit to open writing, 

Wand therefore he may Jot lt down In cryptlc form for himself to decipher 

late!!, when or 1f the Information is needed. The most widely lmown 

15 COl>IFI 9Et~l'IAL 
REF ID:A62856 

co~•Fl9E~~'flifcL AN INTRODUC'l10N TO CRYPTOLOGY - I 

example of such a crJPtogram la 

found In Edgar Allan.Poe's romantic 

tale The Gold Bug. That sort of 

usage of cryptography. however. la 

unusual. There are also examples 

of the use of clplier writing to 

eatabllah priority of discovery. as 

did the astronomers Galileo and 

Huygens. Here's a picture wblcb 

abowB both examples. I suppose I 

should at least mention another 

sort of crJPUc writing famous In 

literary blatory, the diaries of persona such as Samuel Pepys and 

William. Byrd. Tbese are commonly 

regarded aa being 11ln cipher", but 

they were actually written in a more 

or less private shorthand and can 

easily be read without the help of 

oryptanalyala. On the next pap la 

a pap of Pepys diary. 

Now there can be no logical 

reason, point, or pu.rpoae In taking 

c:rLIDll or a ••t.NCL rrm Hqpnl 1 1111'1'11:• llTllllrD: 

Lii• =.rt=.?: ~'IL.":: :r-.:: •1~~~ In ewt'lllled l*'t.\m'9 lrt9Mll•r •ILl:I .. a£.irn.'1.IOll .. u-e •t.un.lan-n 

lam UI• 18\Hn -.n a & a a & & a o c c e c d •••••llllllllll1111••nnnnnn 

~,:..=.'t! ~'~ ~~r',t.:.:,11.r~1r;"::·r:l:L lnr 

.J=~'ti':~1,=• r:~.-~ ... -- .. ~·.:r.·,,:~J~~nr: =necrf:r, , 

Flc.10 

the time and trouble to encipher a.nytblng unless It la expected that some 

other person ls to decipher the cipher some time In the future. Tbla 

means that there must exist some very direct. clear-cut and unambiguous 

relatlonablp between the enciphering and deciphering operatlona. Just 

what such a relationship Involves wlll be dealt wltb later, but at tbla 

moment all that it ls necessary to say la that in enciphering there must 

be rules that govern or control the operations, that these rules must 

admit of no uncertalnty or ambiguity. and that they must be susceptible 

of being applied wltb undeviating precision, since otherwise It will be 

dlff101!lt or perhaps impossible for the decipherer to obtain the correct 

answer when he reverses the processes or steps followed In the enclpberment. Thia may be a good place to point out that a valid or authentic 

cryptanal.Jtlc solution cannot be conaldered as being merely what the 

crJPtanalyat tblnlm or aaya be tblnlm the cryptogram means. nor does the 

solution represent an opir&aon of the cryptanalyst. Solutions are valid only 

lD8ofar as they are obJectlve and susceptible of demonstration or proof 

employing aclentlflcally acceptable methods or procedures. It should 

hardly be necessary to Indicate that the validity of the results achieved 

by cryptanal.Jtlc studies of authentic cryptogram.a rests upon the same A 

sure and well-eatabllabed sclentlflc foundations, and la reached by the W 

same sort of !ogle aa are the discoveries, results, or "ansW8l'S" 

co~~FI 9E~HIAL 16 
" f. 

r -r 

/ ' .. 

,.. 

' ' 

, 

_, ~ 

r. 

,. .,, ,,.. ... 

'I 

',) .. 

, 

• r f• I ... 

.......... 

REF ID:A62856 

W. F. FRIEDMAN eor~f'I O!f~TIAL 

·- /I f- I ,- I 'I J, 

J .., I, ,._ , ., '· .t.f 

•' (\ ,'U.,,f ~ ,.., .. ., .,.. 

•'f t.. r- , ,. .. fl .. 

..., J , ) 

"'"' ( ;. ', "'- 7 f 

' .. ., ,, ' .... -.... ,..,, .... 

'} /I 

..... "- .,,.'" ...... , 11 ....... ... J.L 

... ..., 

" .,.. 

- .,-

I 

' 

J- ., 

' ., 'l- J -· , .,,. I ,· ~ 

, 

-. ' I 

... 

- ,,,. 

,,.., I, J 

.,. 

( 

Ji" 

.. .. ., 

' I 

..... , 

,f J 

r .. :z. ~ 

. - - I ,.., 

r 'I 1.111 ,,~-., t, ; ... _ 

" ·" 'W7 • ...:- ..,. 1' ,. If" I "IP' ./ 1 V '- :rw ,,...,, .. .J , l 

:.-• 

..,,,.. 

., ' J l. ,,,. , ~· 1•1 f'" I 

- ... • ..,. ' J' ...... r' I l'Y - .... ~ ... - I v • ,_ ...,. Jr r· , • e, 

J. .. ' _,,_, - r 

r ' J "'"' , ·-,,_.., ,_ -

' , "?• ,. ~ 

/ i ;i ... ,, 

,, ,. _.., .. , •t'° Ir - - ,_ ~.-

. 

.... '" ,:.., (' ~ J-

; ..... ~~/"' - or- .,., .• ,,. ., .. ~, 

... . ,. .. ,.,;-;.. Ju- .,. ,, ! - ( I 

"' J ' 

" .. J , ,,, ;' -· ' ,,,, . ... .. ~ , ... ..1 .,.. , . r 'll ,, ·- • , ... r, ,~ 

Fis. 11 

17 
REF ID:A62856 

EOtolFI enHIAL AN INTRODUCTION TO CRYPTOLOGY - I 

achieved by any other scientific studies~ namely observation, hypothesis. a 

deduction, induction, and confirmatory experiment. Implied in what IW 

have just saJ.d is the tacitly understood and now rarely explicitly stated 

assumption that two or more, equally competent and, if necessary, 

specially qualified investigators, each working independently upon the 

same material, will aclu.eve identical or practically Identical results. 

Cryptology is usually andproperlyconsideredtobea branch of mathematics, although FranclS Bacon considered it also a branch of grammar 

and what we now call linguistics. Mathematical andstatisticalconsiderations play an ever-increasing and prominent role In practical cryptology, 

but don't let my statement of tins pointfrighten those of you who have not 

had much formal instruction in these subject. We have excellent cryptologists who have never studied more than arithmetic, and some of our 

best ones would bide if you were to go searclung for mathematicians 

around here. What is needed is the ability to reason logically, as the 

mathematician sometimes does, and this ability is found in the most 

curious sorts of persons and places. So those of you who are frightened 

by the words mathematics and statistics take heart--you•re not nearly 

so badly off as you may fear. 

But now to return to the main theme, the place mathematics occupies 

in cryptology, let me say that JUSt as the solution of mathematical problems leaves no room for the exercise of divination or other mysteriouse 

mental or psyclu.c powers, so a valid solution to a cryptogram must 

leave no room for the exercise of such powers. In cryptologic science 

there is one and only one valid solution to a cryptogram, just as there is 

but one correct solution or "solution set" to any problem in mathematics. 

But perhaps I've already dwelt on this point too long, in any case, we'll 

come back to it later, when we come to look at certain types of what we 

may call pseudo-ciphers. 

In the next lecture I'm going to give you a brief glimpse into the 

backgroud or Justory of cryptology, which makes a long and mteresting 

story that has never been told accurately and in detail. The Justory of 

communications security, that is, of cryptography, and the history of 

commumcations intelligence, that is, of cryptanalysis, wluch are but 

opposite faces of the same coin, deserve detailed treatment, but I am 

dubious that tlns sortofhistorywilleverbe written because of the curtain 

of secrecy and silence wlnch officially surrounds the whole field of 

cryptology. Authentic information on the background and development of 

these vital matters having to do with the security of a nation is understandably quite sparse. 

But in the succeeding lectures I'll try my best to give you authentic 

information, and where there's conjecture or doubt I'll so indicate. I musta 

add, however, that in tlns series I'm going to have to omit Jll!UlY highly-W 

interesting episodes and bits of information, not only because these 

COl>~FI 0£1>HIAL 18 
REF ID:A62856 

W F FRIEDMA"l COHFIBEPHIAL 

lectures are of low classification. but also because we won't and can't e;or security considerations, go beyond a certain period in cryptologic 

history. Nevertheless, I hope you won't be disappointed, and that you'll 

learn certain things of great interest and importance, things to remember 

if you wish to make cryptology your vocation in life. 

19 C0~4F19Et~TIAL 
REF ID:A62856 

CONFIBEH'flAL 

An Introduction to Cryptology-II 

BY WILLIAM F FRIEDMAN 

ConfidentuJl 

In tins lecture, the au.tlwr descnbes the earliest attempts at cryptography-from the invention of the art of wn.tin.g t.o Bacon's "Bi-lit.eran.e" 

cipher. 

As I said at the close of the preceding lecture, a bit of history is 

always useful in introducing a subJect belonging to a special and not 

too well known :field; therefore, I'll proceed with some historical 

information about cryptology, which, as you learned before, comprises 

two closely relat.ed sciences, namely, cryptography and cryptanalysis. 

I will repeat and emphasize that they are but opposite faces of the 

same valuable coin; progress in one inevitably leads to progress in the 

other, and to be efficient in cryptology you must know something 

about each of them. 

Cryptography and cryptanalysis probably go back to the dawn of 

the invention and development of the art of writing it.self. In fact, e there is reason for speculating as to which came first-the invention of 

writing or the invention of cryptography; it's somewhat like the question as to which came first-the hen or the egg. It is possible that 

some phases of cryptography came before the art of writing had 

advanced very far. 

I've mentioned the art of writing. As in the case of other seemingly 

simple questions, such as, "why is grass green?", when we are asked to 

define writing we can't find a very simple answer, just because the 

answer 1Sn't at all simple. Yet, Breasted, the famous University of 

Chicago historian and Orientalist, once said: "The invention of 

writing and of a convenient system of records on paper has had a 

greater mftuence in uplifting the human race than any other intellectual achievement m the career of man." There has been, m my 

humble opmion, no greater invention in all history. The invention of 

writing formed the real beginning of civilization. As language distinguishes man from other animals, so writing distinguishes civilized 

man from barbarian. To put the matter briefly, writing exists only 

in a civilization and a civilization cannot exist without writing. Let 

me remind you that animals and insects do communicate-there's no 

A question about that; but writing is a thing peculiar to and found only 

W as a phenomenon in which man and no ammal or insect engages, and 

let's never forget this fact. Mankind lived and functioned for an 

15 -CONFIBEH'flAL 
REF ID:A62856 COt~FIDEt~fl,t\L INTRODUCTlON 'rO CRYPTOLOGY 

enormous number of centuries before wntmg was discovered and there 

is no doubt that, wr1lmg was preceded by articulate speech for eonsbut civ1hzat10n began only when men got the idea of and mvenled the e I 

art of writmg So far as concerns V\Testem or Occidental c1v1hzat1on, 

wntmg is m essence, a means of representmg the sounds of what we 

call speech or spoken language Olher systems of wnlmg were and 

some bt1ll are handicapped by trymg to represent thmgs and ideas by 

pictures I'm bemg a bit solemn about this great mvenbon because I 

want to impress upon you what our studies m cryptology are really 

THE MAGIC 

G_~od -:7~~-: as u l!~er ~· u"ll tiJ--~-now u .!t ~ kno~-- t~ every~ pre .~-::T .~~ 2 U_al] ~~ f}$'h'ZlJ! 2 go th.~!~';]; a .I] of opport' ~ 4' wh1c:b u .}'! 

must £·~~ the i- a th1@>s dj. w'i£- ~. lct-~d' 'a 

spacious ~,J;-<ll>!_tAhave Iii " c. it. here the~ r.81 

a ~in-- ·~ r,:-;J rtf/id. / thCOOg who Nter here 

may: c Then"~ as t~[i!i come 2. B. They c t ... he k~ct of rta they could .Am ~come, IIJ they ~l-~ e 

k1n . d o £• tJw h ose~~t \Tu"m ::-A h~' ~gent~~:~ I ~4"1 

~·~~~s~ who know the ~~of thei·~ of ~1-

~ fTi..!d::!!; wh.o~ ~T new /pe, new ~1lge &nu 

ch~a. V 2 whom U1ey ~come n~. 

This~s soon. no dJE::t till c) is o.ii!r eb b..d' 

a masic I';; a tit1 ~.I hard a. find,~1 2. WJ~ 

!H ·~ a. ! ~· never P,-' never reach: the ~en W of 

gracious s~. "" 

The ~t~( we s~with 6e~ '2 nearby frf':-}.). 

the•c•dJ tll.we "-Q~wave cg /ij!L;- •%.d o.!:fi.'. 

v1.r1rt, a .. NT w-- J. E~E ~ t~ ~s 2 the st or~~ t..Q. .Z. ~~r Ji. ,LhEEE. ','~l " m ~ ... ~~ '( 

lii ~the -~ ~ ~ly fl u &me. ~ ~;;.;we f<j!)nd t;k, ~ e 

Fig. 1. 

COf.,FIE>El.,TIAL 16 
REF ID:A62856 

W F FRIEDMAN CONFIBENJl:itcL 

int.ended to do, namely, to defeat the basic or mt.ended purpose of 

that great invention: instead of recording things and ideas for the 

dissemination of knowledge, we want and stnve our utmost to prevent 

this aim from being realized, except among our own brethren and under 

certain special circumstances, for the purpose of our mutual security, 

our self-preservation And that's important. 

Writing is a comparatively new thing in the history of mankind. 

No complete system of wnting was used before about 3500 B.C. 

Ordinary writing, the sort of writing you and I use, is perhaps an 

outgrowth or development of picture writing or rebus writmg, which 

I'm sure most of you enjoyed as choldren. A rebus contains features 

of both ordinary and cryptographic writing; you have to "decrypt" 

the significance of some of the symbols, combine single letters with 

syllables, pronounce the word that IS represented by pictures, and 

so on. Figure l 18 an example which I have through the courtesy of 

the Bell Telephone Laboratories. See how much of it you can make 

out in half a minute. 

From rebus writing there came in due course alphabetic writing and 

let me say nght now that the invention of the alphabet, which apparently happened only once in the history of mankind, in some 

Middle East Semitic region, 1n or near the Palestme-Syria area, then 

spread throughout the whole of the European continent, and :finally 

throughout most of the world, is Western man's greatest, most 

important, and most far-reachmg invention because it forms the 

foundation of practically all our written and printed knowledge, 

except that in Chinese. The great achievement of the- mvention of 

the alphabet was certainly not the creation of the signs or symbols. 

It involved two brilliant ideas. The first was the idea of representing 

merely the sounds of speech by symbols, that JS, the idea of what we 

may call phonetu:uatwn, the second was the idea of adoptmg a system 

in which, roughly speakmg, each speech sound 18 denoted or represented by one and only one symbol Simple as these two ideas seem to 

us now, the invention was apparently made, as I've said, only once and 

the inventor or inventors of the alphabet deserve to be ranked among 

the greatest benefactors of mankmd It made possible the recordmg of 

the memory of mankind in our bbranes, and from that single invention have come all past and present alphabets Some of the greatest 

of men's achievements we are now apt to take for granted; we seldom 

give them any thought The invention of the art of writing and the 

invention of the alphabet are two such achievements and they are 

worth pondering upon. Where would we be without them? Note 

that among livmg languages Chinese presents special problems not 

only for the cryptologist but also for the Chinese themselves. No 

17 CONFIBEH'fl:AL 
REF ID:A62856 

(;0!1'~Fl9nHh\l INTRODUCTION TO CRYPTOWGY 

Smolog1st knows all the 80,000 or so Chmese symbols, and 1t 1s also 

far from easy to mast.er merely the 9,000 or so symbols actually A 

employed by Chmese scholars How far more simple 1t 1s to use only • 

20 to 26 symbols' Bemg a monosyllabic language, 1t seems almost 

hopeless to try to wnte Chmese by the sort of mechanism used m an 

alphabetic polysyllabic language, attempts along these Imes have 

been unsuccessful and the difficulties m memonzmg a great many 

Chinese characters account for the fact that even now only about 10°(: 

of the Chinese people can read or wr1t.e to any s1gmficant degree 

The spread of knowledge m Chma is thereby much hampered 

We find mstances of ciphers m the Bible In Jeremiah Chapter 25, 

Verse 26 occurs thIS expression "And the Kmg of Sheshakh shall 

dnnk after them " Also, agam m Jeremiah 51 41 "How IS Sheshakh 

taken'" Well, for perhaps many years that name "Sheshakh" reJeremiah 25 ~ 26 " ••• e.nd the king ot Sheshakh shall drink after 

them." 

Jeremiah 51 : 41 "Ho• is Sheshakh taken~ ••• how is Baoylon oecome 

an astonishment among the nations!" 

ii io g a 7 a 5 4 3 2 l 

Rt. 1 TChZVHDGBA 

:> .. ~n" "» tt"T ~~~ 

? 9 d P1! J3!.il? ~I?~ 12 13 14 15 16 17 18 19 20 21 22 

Sh(e)Sh(a)Kh = BBL=- Babel= Babylon 

* * * * * * * * * * * * * 

L'S A,l 

C :.. D,4 

300 

Sh 

600 

*M 

900 

*TZ 

co~mert,.flAt 

30 

L 

60 

s 

90 

Tz 

3 200 20 

G R K 

6 500 50 

v *K N 

9 800 BO 

T *P ' p 

l:_:. I ,lO 

E:. M,40 

Fig. 2. 

18 

2 

B 

5 

H 

a 

Ch 

100 10 l 

Q I A 

400 40 4 

Th 14 D 

700 70 7 

•N ·o z 

\:.:_ = Q, 1.00 

E.=Th,400 
REF ID:A62856 

W F FRif:DMAN 

mamed a myotery, because no such place was known to geographers 

or historians But then it was discovered that if you write the 

twenty-two letters of the Hebrew alphabet m two rows, eleven m one 

row and eleven m the other, as m F1g 2, you set up a substitution 

alphabet whereby you can replace letters by those standmg opposite 

them For example, "Shm", is represented by "Beth" or vice versa, 

so that "Sheshakh" translates "Babel", which is the old name of 

"Babylon " ' Hebrew then did not have and still doesn't have vowels, 

they must be supplied This is an example of what, is called 

ATHBASH writmg, that is, where Aleph, the first letter is replaced by 

Teth, the last letter, Beth, the second letter, by Shm, the next-to-thelast, etc By shdmg the second row of letters one letter each time 

there are eleven different cipher alphabets available for use The old 

Talmudists went m for cryptography to a considerable extent 

Incidentally, m ment1onmg the Bible, I will'add that Daniel, who, 

after Joseph m Genesis, was an early mterpreter of dreams and therefore one of the first psychoanalysts, was also the first cryptanalyst 

I say that he was an early psychoanalyst, because you wtll remember 

that he mterpreted Nebuchadnezzar's dreams In the Bible's own 

words, "Nebuchadnezzar dreamed dreams, wherewith lns sp1nt was 

troubled, and sleep brake from h1m" But, unfortunately, when he 

woke up he JUSt couldn't remember those troublesome dreams One 

mornmg he called for his wise men, magicians, astrologers, and 

Chaldean sorcerers and asked them to interpret the dream he'd had 

durmg the precedmg mght "Well, now, tell us the dream and we'll 

try to mterpret it", they said To which Kmg Nebuchadnezzar 

exclaimed, "The thmg is gone from me I don't remember it But 

it's part of your JOb to find that out, too, and interpret it And if you 

can't tell me what the dream was, and mterpret it, thmgs will happen 

to you" What the kmg asked was a pretty stiff assignment, of 

course, and it's no wonder they fatled to make good, which irked 

Nebuchadnezzar no end Kmgs had a nasty habit of chopping your 

head off m those days if you failed or made a mistake, Just as certam 

arbitrary and cruel despots are apt to do even m modern ilmes for 

more mmor mfract1ons, such as not followmg the Party Lme So m 

thib caoe it comes as no surprise to learn that Nebuchadnezzar passed 

the word along to destroy all the wise men of Babylon, among whom 

was one of the wise men of Israel, named Daniel Well, when the 

Kmg's guard came to fetch him, Daniel begged that he be given Just 

a bit more time Then, by some act of divination, --the Bible simply 

says that the secret was revealed to Damel ma night VISion-Daniel 

was able to reconstruct the dream and then to interpret it Daniel's 

reputation was made Some years later, Nebuchadnezzar's son 

Belshazzar was giving a feast, and, durmg the course of the feast, m 

19 co~~FIDE~HIAL 
REF ID:A62856 

co~~FIE>HfFIAL INTRODUCTION TO CRYPTOLOG y 

the words of the Bible, "came forth fingers of a man's hand and wrote 

over agamst the candlestick upon the plaster of the wall " The hand 

wrote a secret message. You can imagme the spme-chilhng scene. 

Belshazzar Wab very much upset, and JUSt as his father did, he called 

for his WISe men, soothsayers, Chaldean sorcerers, magicians and so on, 

but they couldn't read the message Apparently they couldn't even 

read the cipher characters' Well, Belshazzar's Queen fortunately 

remembered what that Israelite Darnel had done years before and 

she suggested that Darnel be called mas a consultant Darnel was 

called m by Belshazzar and he succeeded m domg two thmgs He 

succeeded not only m read.mg the wnlmg on the wall "MENE, 

MENE, TEKEL, UPHAH.SIN", but also he was successful m deciphermg the meamng of those strange words His mterpretabon 

"Mene" - "God hath numbered thy kmgdom and firnshed it " 

"Tekel" - "Thou are weighed m the balances and found wantmg" 

ingernuty of the most expe1t scholars ot the Bahylo111an court 

Of course 1t cannot be denied, as Lagarde has po111ted out, that 

the ideograpluc values of these four words, •count, m111a, shekel 

and part,' were undoubtedly signs with which any educated 

Babyloman was familiar (' Mitthe1lunge11,' 1 v 36-l) If, ho\\-

ever, we suppose that the ideograms were written close together 

\Vlthout any division between the md1vidual words, a style of 

writing we often meet with in the cuneiform mscr1pt1ons, thus 

1t would be just e.s ha.rd to read as e. 1 ebus and would pnzzle 

the most skillful decipherer The difficult) would ha\e bee11 

still more mcreased if the ideograms had been grouped m some 

unusual we.y, severing the natu1al connect1on of the component 

elements, for example, thus· 

If the signs had been w11tten 111 this manne1 1t would have 

been almost impossible to a1 r1 ve at then trne mean mg The 

first combination, SID-MA, m1gl1t l1ave some fifteen different 

meanings, the second group, N A-TU-U, mtgl1t s1g111f.} '1s fit' 

or 'suitable,' while the third and last, BAR-BAR, 1s capable 

of explanation m a var1et) of ways" Of com~e, as soon as 

qne is told the meamng of the C'ombmat1on, the sentencP at 

once becomes clear. ' 

Fig. 3. 

eo~mDHHIAL 20 
- - - ------------------

REF ID:A62856 

W F FRIEDMAN EOUFIDEtHIAL 

"Upharsm" --- "Thy kmgdom shall be divided and given to the Mede!'l 

and Persians " Apparently the chap who did the handwritmg on the 

wall knew a thmg or two about cryptography, because he used what 

we call "vanants", or different values, for m one case the last word m 

the secret writmg on the wall is "Upharsm" and m the other it is 

"Peres", the commentators are a bit vague as to why there are these 

two versions of the word m the Bible. At any rate, Babylon was 

fimshed, Just as the mscnpt1on prophei,nzed, it died with Belshazzar 

I thmk this cur10us Biblical case of the use of cryptography is 

mterestmg because I don't thmk anybody has really found the true 

meanmg of the sentence m secret writing, or exp]amed why the writmg 

on the wall was unmtelhgib1e to all of Belbhazzar's wise men Figure 3 

is supposed to give the best explanation of the emgmatical sentence 

that has always been considered one of the most obsc..ure of the many 

difficult scriptural. passages which have awakened the mterest and 

baffled the mgenmty of scholars You see that this savant thmks 

that the cuneiform ideograms were written without any division between the mdividual words, so that the sentence "would be 3ust as hard 

to read as a rebus and wou1d puzzle the most skil1ful decipherer " 

He goes on to bay "The difficulty would have been stdl more mcreased 

if the ideograms had been grouped m some unusual way, severing the 

natural connection of the component elementb Jf the signs had been 

written m this manner it would have been a1most imposbible to arnve 

at their true meanmg" But why could Damel read and mterpret the 

wntmg when his competitors couldn't? This our savant doesn't 

explam Another savant offers as his explanation of the mystery the 

followmg hypotheslS That the wordb were written m columni,,, as 

i,,hown, and that Damel m solvmg the mystery read downwards or 

rather down, up, down Thu;, explanation doesn't satii,,fy me any 

more than the other one 

Probably the earhest rebab]e mformat1on on the use of cryptography 

m connection with an alphabetic language dates from about 900 BC, 

Plutarch mentiomng that from the time of Lycurgus there was muse 

among the Lacedemomans, or ancient Greeks, a device called the 

scytale This device, which I'll explam ma moment, was defimtely 

known to have been used m the time of Lysander, which would place 

it about 400 BC This is about the time that Aeneas Tact1cus wrote 

his large treatise on the defense of fortification, m which there is a 

chapter devoted specifically to cryptography [n addition to mentionmg ways of physically concealmg messages, a pecuhar sort of cipher 

disk is described Also a method of replacing words and let.tars by 

dots is ment10ned 

21 cotimDEtHIJ*\L 
REF ID:A62856 

co•~FIBEtHIAL INTRODUCTION TO CRYPTOLOGY 

Figure 4 1s a picture of the scytale, one of the earliest cipher devices 

history records The scytale was a woodencyhnderofspec1ficd1menFig. 4. 

s10ns around which they wrapped spirally a piece of parchment or 

leather, they then wrote the message on the parchment, unwound 1t, 

and sent 1t to its destmabon by a safe courier, who handed it over to 

the commander for whom 1t was mtended and who, havmg been provided with an 1dentically-d1mensioned cylmer, would wmd the strip 

of leather or parchment around his cylmder and thus bnng together 

properly the letters representmg the message This dmgram may 

nol be accurate I don't thmk anyone really understands the scheme 

The wntmg was done acrosi:. the edges of the parchment, accordmg 

to some accounts, and not between the edges, as shown here Incidentally, you may be mterested to learn that the baton which the 

European field marshal still carries as one of the ms1gma of his high e 

ofhce derives from this very mstrwnent 

We don't know much about the use of cryptography by the Romans, 

but 1t is well known that Caesar used an obviously sunple method, all 

he did was to replace each letter by the one that was fourth from 1t m 

the alphabet For example, A would be represented by D, B by E and 

so on Augustus Caesar 1s said to have used the same sort of thmg, 

only even more simple each letter was replaced by the one that 

followed it m the alphabet Cicero was one of the mveniors of what 

is now called shorthand He had a slave by the name of Tyro, who 

wrote Cicero's records m what a1·e called Tyroman notes Modern 

shorthand is a development of Tyro's notation system 

In Fig 5 we see some cipher alphabets of olden times, alphabets 

used by certam h1stor1cal :figures you'll all remember The first cipher 

alphabet m this figure was employed by Charlemagne, who hved 

from 768 to 814 A D The second one was used m England durmg the 

reign of Alfred the Great, 871 to 899 The third alphabet is called 

ogam writing and was used m ancient Ireland The alphabets below 

that were used much later m England the fourth one by Charles the 

First, m 1646. the fifth, the so-called "clock cipher", was used by the A 

Marquis of Worcester m the 17th Century, finally, the last one y.ras W 

used by Cardmal Wolsey m about 1524 

COt~FIBEt~flAL 22 
REF ID:A62856 

W F FRTEDMAN CONF19ENTIAL 

h I /" .J' " k d t r ~ 11111 R§ ) r 11 o ,. ,. a. fl" m "'~ "'- 1 II tll !Ill II II I I I I I'll I 11 Iii 1111 11111 • w-*~ hw I II Ill 1111 11111 X 0 a 1!!l 

ul>e d, / t;h ' ,, / \ 

1 k I"'" pp 'Ir .r f v w.:r: yr. 

~/11 I 1,-, I r r '/ y - ' _, 

"f. c <I e J !I""~ of- I m.n. op 'Ir.rt u. w .c y z 

G0~080~QG00080QQG0~080QG 

N.l.wnH,14nlo1tH""'"'/"'""""*'""'.6 

J1.,A,,,.f-,,,.J.. f/,,"';1N>l"~"""""'f11,,,J.-·J, 

...... A.wo1·-·"""-"~·~"""'--,;t;~.a;...'.~k 

.~....e~•...M .... I ......... ~ 

lo~,~.," fJ ~--~ ........ ~._,..,-t - ...... L -ti~ =11 ~ J,; r#I ...,.-~ ... ~-'IZ•f' 

--..-7"--.,.." 10\\.,...,l\=cl";s:dd'"Q.,N '=.z..,1(4 ..... ._ =.r=J.,..~ 

- - ::::!: - Z ~ ~ ~J ==ii~//~\""'" J_...-\,.A.~S =,..A>;.t"~ %'_,....'\-~ -.,.,.. !] 

In the Middle Ages cryptography appears first as a method of 

concealmg proper names. usually by the sunple substitution of each 

A letter by the next one m the alphabet, Just about as Augustus Caesar 

W did hundreds of years before At other times the vowels were replaced by dots, without changing the consonants--a method that was 

ui.ed throughout Europe to about 1000 A D , when letters began to be 

replaced by various sign'>, by other letters, by letters from another 

language, by runes which are found m abundance m Scandmavia, and 

by arbitra1·y symbols Figure 6 is an example of a rumc inscription 

on a btone that stands before Gupsholm Castle near Stockholm, 

Sweden The word rune means "secret" 1 

W1t.hm a couple hundred years the outlines of modem cryptography 

began to be formed by the beci-et correspondence systems employed by 

the small Papal States m Italy In fact, the real begmnmgs of systematic, modern cryptology can be traced back to the days of the 

early years of the 13th Century, when the science began to be extensively employed by the pnnces and chanceries of the Papal States 

m their d1pJomahc relations amongst themselves and with other 

cow1tries m Europe The necessity for secret communication was 

first met by attempts 1nspired by or derived from ancient cryptography, as I've outlmed so far There was a special predilection for e ~wel ~~~titut1on but thei-e appeared about this time one of the 

1 The author's capt.10n "A couple of old ru1ns"-Ed 

23 co~~FIBEt'4flAL 
REF ID:A62856 (QMFIBEt~'fllcl INTRODUCTION TO CRYPTOLOGY 

elements which was later to play a very prominent role mall cipher 

systems, an element we now call a syllabary, or a repertory. These 

were hsts of letters, syllables, frequently-used parts of speech and e 

words, with additions of arbitrary equivalents for the names of 

persons and places. There is stall m existence one such syllabary and 

hst of arbitrary eqmvalents which was used about 1236 A D. and there 

are other examples that were used 10 Venice m 1350 

Fig. 6. 

Among examples of ciphers in medieval cryptography is a collection 

of letters of the Archbishop of Naples, written between 1363 and 1365, 

m which he begins merely with symbol substitutions for the vowels 

and uses the letters that are actually vowels to serve as nulls or nons1gnificant letters to throw the would-be-cryptanalyst off the right 

track. As a final development, the high-frequency consonants L, M, 

N, R, and S, and all the vowels, are replaced not only by arbitrary e 

symbols but also by other letters. 

COt~FIBEMTIAL 24 
REF ID:A62856 

W F. FRIEDMAN COHFIBENflAL 

About 1378 an experienced cryptologist named Gabriele Lavinde of 

Parma was employed as a professional by Clement VII and in the 

Vatican Library there is a collection of ciphers devised and used by 

Lavinde about 1379. It consists of repertories in which every lett.er 

is replaced by an arbitrary symbol. Some of these ciphers also have 

nulls and arbitrary equivalents or signs for the names of persons and 

places. There is a court cipher of Mantua dated 1395 that used this 

system. 

At the beginning of the 15th Century the necessity of having 

variants for the high-frequency letters, especially the vowels, became 

obvious. Figure 7 JS an alphabet of that period which is mteresting 

because it shows that even in those early days of cryptology there was 

already a recognition of the basic weakness of what we call single or 

,. J~f A , . t ,1 / .. ir '""' ,41. 1irr ,,., ''I q~ 'o .11.t _J,,, .us '"·'J'J. •ft ., 

o '":411 .... ~,/, (' .q. f,/ }• fJt", ~' f:.l J, & 14' 1 t;. I • " 6/f" // l 

.& ''"·''·' ..: ... ,,' t ,..,, ,..,, "" ~,,, 6,,1 ,/ ~ /'... 

" - ~. 44. II.I; I~". IJft-.nl. DI. J.f~ ll:/", a"· .. .l. 4

• .. ,,. , 40, tl.t..'li': .S"jl. ~I 

C:o41;11,,,.r,,.,.. • 

,'J) .U.?f. 14,llJ,M,l.U,Jb, ,,,.il'..Ut' 't44rl1, .f.U.-t,.,."44)'j,Af,1.11f 

l. r.•, t.;,,, c.'~ t; " r.-,. "'· · ,/ 

E .~o :114 21, 2f..Jl,.•J' .n: .. ,, A1.rr.PJ.•~.1.a.11. "~· •1.111,llJll,llll-, 114,,,., 

• m. O~l""-R"Vl't" """·'"?.~1114/166, Ut """'- ~,,,,,,,.,_.n~ --~ ........ t U1 ~,,,. a11 .• --.~1.n..lf4~·~_.,.,i_.,,., •l.\.t//,,~ 1J11 .. ~.1•v,. 

' •

1

•• "'"' ,,..J,J).f., ""J14 .. ~1,,,,, .• .,,~ .. ,,,,,,. $.fJl',#..f't .ft.1.,11 

..t4:f,.f.f.,,.,.,.,...,.,. ..... ,.lw.--.. "tl'IV-.Nf/ ... p ...... ~J, 

Ml. ,.,t, _..,., "U.1»e.11t ~..1:1,,..ut"~ ~ Nir • .Hi,,.,.,.,_ ni 

~· A~Sf• • .-... ~4fi~ "-. 41,. ~~,G44i(4f . .ir.., ~I~ .-4, 9, .... . • . F"' ~ 

r-. • .,.-...,,..~ •••· 

Fig. 7. 

monoalphabetic substitution, that is, where every letter in the plaintext message is represented by another and always the same letter. 

Solution of this type of cipher, as many of you may know, is accomplished by taking advantage of the fact that the letters of an alphabetic language are used with greatly differing frequencies. I don't 

have to go into that now because many of you, at some tune or other, 

have read Edgar Allan Poe's "Gold Bug", and understand the principles of that sort of analysis. It is clearly shown in the figure that the 

early Itahan cryptographers understood the fact of varying freA. quencies and introduced stumbling blocks to quick and easy solution 

• by having the high-frequency letters represented by more than a 

25 CONABENflAL 
REF ID:A62856 

eot~FIBOHl:AL INTH.ODUCTION TO CHYPTOLOGY 

single character, or by several charac,ters, as you can see I will add 

that the earliest tract that the world possesses on the subject of 

cryptography, or for that matter, c.ryptanalysis, is that which was e 

written m 1474 by a Neapolitan, whose name was Siew Simonetta 

He set forth the basic prmciples and methods of solvmg ciphers, 

simple ciphers no doubt, but he descnbes them and their solution m 

a very clear and concise form 

Cipher bystems of the type I've described contmued to be improved 

In Figure 8 i& shown what we may call the first complete cipher system 

of this c;ort There are subbtitution symbols for each letter, the vowels 

have several equivalents, there are nulls, and there is a small hst of 

arbitrary symbols, such as those for "the Pope", the word "and", the 

conJunctlon "with", and so on This cipher, dated 1411, was used m 

Vemce, and is typical of the ciphers used by the Papal chancenes of 

those days 

A B C 0 E F G H,11L MN 0 1P QR STU v NULLE &I = Paoa 

1•\'7)1'2 ~ I? J. !'° •-14 9 i 5 q = 13' I 5 : 5 b c () ~ .. =et 

O• * X -(>1 ( 'H H ;,--:_~1 §__ R =con 

Mo + T· I I I I \ :r. :t "' 0 l' :i, cp :quo 

Fig 8. 

The step remammg to be taken m the development of these ciphers 

was to expand the "vocabulary", that 1s, the hst of equivalents for 

frequently-used words, and syllables, the names of persons and places, -

parts of speech, and so on Tlus step was reached in Italy dunng the · 

(;Q~tFIBEtHIO?'\L 26 
~ 

........ """ 

,,._.. 

:q· 

p'4!.n 

~ 

...., 

_, 

~· 

W. F. FRIEDMAN 

REF ID:A62856 

eot~FIDEH'FIAL 

t· 

i 'tfl ,< "ft. ,., t t' u ~·.., " r ~ 'V 

.. ,....,, y h g -~'i;-*'~ ,, ft < ... " ' ~- ~ t;-,~r.: ... 

l ·' 

(f 1"I ' " 

f' ~~ii:~~\ ~~vr4 -1,.., .~.~ ~ ... ' ,1 ')i,,.,."" (. h -..\ ~>it#}••"'<~ f1t\ 

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··-1i..,1.-.,..,,.,~· t:,..'/'f' ~ t "'"".,.du.. f ,.,~\,"\ .,,,.~,(' .~ ....... ., ... f>o1~ 

,. r:: ~ ·""".... f"" l~ Vt.~~ >f<~l ' 

c '""~ ..... ~· '' ~·~·· ("~lcii.mu<tflu~ ~Hut: 

(' .111},,,..-,,.~ ,...,,.~·· 

$•-"1:'N<JI' ' • p,.,..,cJum• 

".;_,, .. ,,,.'(IN".... ~: 

-tL..oaM!n4- ' f~iHb 

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.. ·, ... ';:,,,...,,.., 

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i:""'"'' 

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Fig. 9. 

~tln~ f $«-H!l.r-tn 

$..£au 

~ 

::.'-tmttl 

~ .. ' s-. 

t'(· M· 

:-' u. 

~~ ., . 

27 COt~FIBEN'flAL 
REF ID:A62856 

CONFIBENflAL INTRODUCTION TO CRYPTOLOGY 

~~~- .• -~ . ~;ii, .. 

-. "'"ii h ... ):, . ..,-: ·.:, -.,.. ~- .r .,,, '>' .t.. ; 

t 

i~1 • ...;. i.~ -ff. -w- ....,.._ 

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.:.-... ,~~ ... we. .C..n:-~-:._. 

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FJs.10. 
REF ID:A62856 

W F }'RIEDMAN eo~~FIBOHIAL 

first half of the 15th Century and became the prototype of diplomatic 

ciphers used m practically all the states of Europe for several centuries 

One of 70 ciphers collected m a Vatican codex and used from about 

1440 to 1469 is shown m Figure 9 Note that the equivalents of the 

plamtext items are Lahn words and combmatlons of two and three 

letters, and that they are hsted man order that 1s somewhat alphabetical but not stnctly so I suppose that by constant use the cipher 

clerks would learn the equivalents almost by heart, so that an adherence to a strict alphabetic sequence either for the plamtext items 

or for their cipher equivalents didn't hamper their operahono:; too 

much In Figure 10 there is much the same sort of ar1angement, 

except that now the cipher eqmvalents seem to be digraphs and the&e 

are arranged ma rather systematic order, for ease m enc1phermg and 

dec1phenng Now we have the real begmnmgs of what we call a 

one-part code, that is, the same hst will serve both for enwdmg and 

decodmg These systems, as I've said, remained the prototypes of 

the cryptography employed throughout the whole of Europe for some 

centuries The Papal States used them, and as late as 1793 we find 

ex. J, c. d e. J v ~ oe "' Ji. E. 

'Y .... -w. 0 

I~ 'P 1 'l" ~ t. 

)It' ':I 'lf ~ "V" 

Ii' -& 

• 2• 

pa. J.e J,, J.o ... , 

" 'U " "" V+ 

J.a. cl.c! d~ J.o du , 

...... .... ...... .... j'!z f'e y .. r f'" - ci ... .... ..... "'+ 

)a. /e ]1 Jo , .... ,_. •' I. 2- 4 :t.+ 

,,_ ....... ..... i.n&o 1,,.... 

<i "t 't 4e. 't+ 

~ pe J3:1. /'O pu. 

' ' ' ,_ '+ ,.,,. toe :r1 ,,... 1-U 

~ 1 I ~ :ft. 

14. te. ~ to tu. 

'+ 9 ,_ ' ,. 

g J,. .2 

1 t "" -sa 

tf 

v x y 

~ A Xt- tf 

10 ,,. 

l- . n. 

ll 4 8 

& 

'%. 

Ve 

ar.--

IJ~ ... ~ se:rtU& fo4e14 Z... letnu,11...,,.,..., 

0 C&ree.f:Bre'J>f.&&e f:UNCl'7eft ILllC 

rA'JG lA>'.f'.ul.l.or 'Ju .. - - ..._ 

t-.o e ...... 1.e f001" 2U& O .;;. , 9 '!'•P :ll' P 1 

t 1"" SS 

Fig 11. 

29 (Ot~Flf>fttHIAL 
REF ID:A62856 

EONFIBEtffll*<L INTRonuc rmN To cH.YPTOLoc;v 

them used m France I wish here to mention spec1fical1y the so-called 

Kmg's General C1pher used m 1562 by the Spamsh Court It is 

shown m Fig 11 

But there were two exceptional cases which show that the r1g1dity 

of cryptographic thought was now and then broken durmg the four 

centuries we have been talking about m this brief historical survey 

Some of the Papal ciphers of the 16th Century and those of the 

French Court under Kmgs Louis XIII and XIV exemplify these 

exceptions In the case of these French Court ciphers we find that a 

French cryptologist named Antomo Hos.c;1gnol, who was employed by 

Cardmal Richelieu, understood qmte well the weaknesseo of the onepart code and syllabanes It was he who, m about 1640, introduced 

a new and important improvement, the idea of the two-part code or 

syllabary, m which for encoding a message the items m the vocabulary 

are hsted m some systematic order, nearly always alphabetical, the 

code equivalents, whatever they may be, are asi:ngned to the alphabehcally-hsted items m random order Th10 means that there must 

be another arrangement or book for ease m decodmg, m which the code 

equivalents are hsted m systematu, order, numerically or alphabetically as the cabe may be, and alongside eac.h appears its meanmg 

m the encodmg arrangement, or book The s1gmficanc.e of this 

improvement you'll find out sooner or later Codes of this SOl t also e 

had var1ants--Hoss1gnol was clever, mdeed One such code, found m 

the 1691 correspondence of Loms XIV had about 600 items, with code 

groups of two and three digits Not at all bad, for those days' 

Now this sort of svstem would appear to be qmte secure, and I 

suppose it was mdeed so, for those early days of cryptog1aphic development-- but it wasn't proof agamst the cleverness of British 

brams, for the emment mathematician John \.Valhs solved messages 

m it m 1689. Never underestunate the British m this sc1enc.e--as 

we'll have reason to note m another lecture m this series "' 

French cryptography under Kmgs Louis XV and XVI declined, 

reachmg perhaps its lowest level wider Napoleon the Great It is a 

fact that m Napoleon's Russian enterprise the whole of his army used 

but a smgle code book of only 200 groups, practically without variants, 

even for the high-frequency letters Furthermore, not all the words 

ma message were encoded--only those which the code clerk or the 

writer of the message thought were important It's pretty clear that 

the Russians mtercepted and read many of Napoleon's messages -this 

comes from categoncal statements to this effect by Czar Alexander I 

• Ofhcml deuphermg of foreign commurucationa by BritJSh cryptologlllts cane 

be tra<'ed back to about the vear Hi25, if not earher 

CONFl9ft'Hll'cl 30 
REF ID:A62856 

W ~' FRIEDMAN COt'4f IBEt'4'fl AL 

himself We won't be far wrong m behevmg that the weaknesses of 

Napoleon's crypto-commumcations formed an important factor m 

Napoleon's dISaster A hundred and twenty-five years later, Russian 

ineptitude m cryptographic commumcations lost them the Battle of 

Tannenberg and knocked them out of World War I 

The other 16th Century Papal ciphers that constituted the second 

exception to the general similarity of cryptographic systems of those 

days were quite different from those I've shown you In this exception the ciphers were monoalphabetic. but some letters had the same 

eqmvalent, so that on decipherment the context had to be used to 

decide which of two or more possible plamtext values was the one 

meant by each cipher letter One such cipher used by the Maltese 

CIPHER OF THE INQUISITOR OF MALTA (1585) 

(From SACCO, MANUALE DI CRITTOGRAPHIA, 1947) 

chiaro - A,T E,F 

cifra - ¢ 3 

Nulle 1,8 

I,G O,D 

5 4 

U,V,B 

2 

C,L,N 

6 

M,R P,S,Z 

9 7 

chiaro - qua que qui quo che chi non quando perche,et,per 

. e cifra - 7 9 6 2 4 5 3 ¢ 1,8 

Seguono varie voci, cifrate con un gruppo di due cifre 

tramezzate da un punto, es il Papa= 2 7, il Re di Francia= 

3 2 

Flg.12 

lnqws1tor m 1585 1s shown m Fig 12 You'll note that the d1g1t 0 

has two values, A and T, the digit 2 has three values, U, V, andB, and 

so on There were two digits used as nulls, 1 and 8, digits with dots 

above them stood for words such as Qua, Que, Qm, and so on 

Figure 13 shows how a mes...age would be enciphered and deciphered 

A bit tricky, ISn't it? Many, many years later Edgar Allan Poe 

descrtbes a cipher of this same general type, where the decipherer must 

choose between two or more possible plamtext equivalents m building 

up hIS plam text, the latter gmdmg the choice of the nght eqmvalent 

The trouble with dus sort of cipher is that you have to have pretty 

smart cipher clerks to operate 1t and even then I unagme that m many 

places there would be doubtful decipherments of words It wasn't 

really a practical system even m those days, but it could, if used 

skillfully and with only a small amount of text, give a cryptanalyst 

.lenty of headaches But such systems didn't last very long because 

of the practical difficulties m usmg them 

31 c:;QNF19EN'ffAL 
REF ID:A62856 

eot~FIBEtHIAL INTRODUCTION TO CRYPTOLOG"'t 

Esempio di cifratura 

criaro - S P E R 0 C H E 0 G N I C 0 S A S I A 

cifra - 7 7 3 9 4 4 4 5 6 5 l 6 4 7 0 8 7 5 ¢ c~e sara trasmesso tutto unite, senza spazi 

Esempio di decifratura 

cif ra 4 5 l ¢ 2 ¢ 4 l 4 ¢ 9 4 8 9 5 6 2 0 4 l ¢ 2 

IQ I 

decifra ~ D G 

I 

A U A 0 

T B T D 

v 

0 A M 0 

D T R D 

M I C U A 0 

R G L B T D 

NV 

AU 

T B 

v 

criaro D I T U T 0 D A R 0 M I N U T 0 A V 

cifra 5 7 4 

;r P o 

decifra ~GS D 

l z 

l 

ET 

PER 

PER CHE 

chiaro I S,O PER 

4 5 6 5 l 6 4 9 5 3 9 3 8 

0 I C I 

D G L G 

N 

C 0 M I E M E 

N D R G F R F 

L 

0 G N I C 0 R I E R E 

Fig. 13. 

The first regular or official cipher bureau m the Vatican was estabhshed m about 1540, and m Vemce at about the same time, about 

one hundred years before a regular cipher bureau was established m e 

Ftan('e by Cardinal H.icheheu It is mterestmg to observe that no 

new or remarkable ideas for cryptosystems were developed for a 

couple of hundred yemi. afte1 the complex ones I've described as 

havmg been de\<eloped by the va1·ious Papal cryptologistb One-part 

and 1wo-part i.yllabanes and simple or complex ones with vanants 

were m use for many decades, but later on, ma few cases, the code 

eqmvalento:, we1e supe1enciphered, that lb, the code groups formed the 

text for the apphcat10n of a cipher, generally by rather •nmple systems 

of additives Governmental codes were of the two-part type and 

were .;;uperenuphe1ed bv the more soph1<;tu,ated countries 

The firi.t book or exteni.1'Ye tteat1se on cryptography 1s that by a 

German abbot 1Mmed Tr1them1m., who published m 1531 the first 

\<olume of cl p!Anned 4-volume monument.al work I said that he 

planned to pubhsh four 'volume~, but he gave up after the third one, 

beeau.;;e he wrote i:.o obi:,cmely and made ouch fantastic clauns that he 

wa., Lharged with bemg m league with the Devil, which was a rather 

dange1 oui:. a ....,oc1.ition m thoi.e or even m the.;;e days They didn't 

burn Trithenuui. but they did burn his books Figure 14 illustrates 

that the neC'e::...o..,1ty for secrecy m this busme-;o was recogmzed from the 

ve1y earhe~t dc1ys of eryptology and certamly by Tr1themms Her~ 

10:, the &01 t of oath that Trilhemms recommended be admm1stered to 

EOt~FIBEtHIAL 32 
REF ID:A62856 

W F FRIEDMAN CONFIBEtHIJAcl 

students in the science of cryptology All of you have subscribed to a 

A somewhat similar oath, but we now go further and back up the oath 

9 with a rather strict law You've all read it, I'm sure 

!Pe ~if~ian Q)tttb ~-7- ,gibenJW ,_, 

•o~a.n.ne1S ~ iti)emlus 

llt 

~o.ol\ll,ti~apttr XXIV, .of ~ .. ~if~ano~'Il\J3l)la' . 

.Fig. 14. 

33 eot~FIBENTIAL 
REF ID:A62856 

COll'IFIE>EtHIAL INTRODUCTION TO CRYPTOLOGY 

We come now to some examples from more recent history. In 

Fig. 15 we see a cipher alphabet used by Mary, Queen of Scots, who 

reigned from 1542 to 1567 and was beheaded in 1587. In this con- e 

nection it may interest you to learn that question has been raised as to 

whether the Queen was "framed" by means of this forged postscript 

(Fig. 16) in a cipher that was known to have been 1:1Sed by her. 

Fig.10. 

"1111·: H1K1a·.11 1•11Sl"Sl"IUl'I. \\"II II 1'1111.l.ll'S"S E:\IJllRSl·:\IE'.\I 

Fig. 16. 

COtf FIE>EtHIAL 34 
REF ID:A62856 

W F FRIEDMAN CO~IFIE>E~nlAL 

The Spamsh Court under Phillip II, in the years 1555 -1598, used a 

great many (,'lphers and here's one of them (Fig 17) You see that it 

is quite complex for those early days and yet ciphers of this sort were 

solved by an emment French mathematician named Vieta, the father 

of modem algebra In 1589 he became a Councelor of Parhament at 

Tours and then Privy Counselor While m that JOb he solved a 

Spamsh cipher system usmg more than 500 characters. so that all the 

Spanish dispatches falhng mto French hands were easily read Phdhp 

C:.lra st••nd im 

; .x.e X.'L k.O :It.\& 'Y"' 'j• ':fl 'JO yu. 

8'+ i a''fl'" :("Y!. r..' ·~ ~ h., ~, 

'La- x.e 'X,.'I. LO l.U plG He p~t JlP 'J,W. ~ 

I If- I ... 1-e 11. n: n 'lj, ... 11J..1 

~ .,,~ lm:. pro I~ cii.a. che. e7a.r. chD chi.& ~ *- TV .,,... ()' ()f. ";)" (>c- (>e 

cl.a cZe cl ... cl.o lelu C.';G CPe C1'1. C'l"O CPU 

1. !" ~ g.. ~ j. S! i 9..r 9... 

~NI cl.re el.re d.ro bl~ f ~ fle. flt. flo flu. ,;. B+ .g: .g... -3-e 7 7+ 1 .,,. :!!-

fro. I foe lr;i. 1/-r-G If-jlor. fle :Yh ~lo ~Lu. 

j. 7+ t ..,.. te ~' 6i- 6" ~ G-e 

7' ~ ¥' -'l"O 

~· ~la ~Ill jilt. ifolo 'f''lu. 

~ =f.e. g. ~ ci ig.. ~ 

1IJ- ,_ :?':' pro fl7U troc. tH! ~r~ tPO 

'fl Ett- -a: ~ ~ -a ~ ~I oc.,t •Z: ... z: ot ul a.t"L e.~ ';ft Oft, .......... 1 , i r+ ~ ~ 'dt. tr ~ (T err- ~ 

a.r- er 1.1"" or u.r GU •1 t-1 01 U4 

.f '1+ -i- -1-o- +e I . 'U u+ \) ~ ve 

~ k.,. Tnr ~or ki .. Ja.s ~I ~&( /,or ~Uf' 

K 6+ J,' ~ J-e r y+ ? F re. C41'" ce,.. e..Lr 

~' e..w CCU ees Cl.I c.os -u.1 

:;;/. ~ 4). --.. ........ 

~ D' D+ D Der Dot 

Fig. 17. 

was so convmced of the security of his ciphers that when he found the 

French were aware of the contents of hIS cipher dISpatches to the 

Netherlands, he complamed to the Pope that the French were using 

sorcery agamst him V ieta was called on the carpet and forced to 

explam how he'd solved the ciphers m order to avoid bemg convicted 

of sorcery, a serious offense. 

The next cryptologist I want you to know somethmg about IS 

another Italian savant who wrote a book, publIShed m 1563, m which 

35 eot~Flf>!l~TIAL 
REF ID:A62856 

co~mBEtHIAL INTRODUCTION TO CRYPTOLOGY 

he showed certain types of cipher alphabets that have come down m 

history and are famous as Porta's Alphabets Figure 18 is an example A 

of the Porta Table, showmg one alphabet with key letters A or B, W 

another alphabet with key letters C or D, and so on I don't want to 

go mto exactly how the key letters are used, it is sufficient to say that 

even to this day cryptograms usmg the Porta alphabets are occas10nally encquntered 

That Porta's table was actually used m official correspondence is 

shown by Fig 19, which IS a picture of a tabJe found among the state 

AB a b c d c f g hi 1 I Im 

n 0 "P q ~ s tvx :.VI Z IU 

CD a b c d e f g"h i 1 m 

7. n 0 IP q r s l v x y 

EF a b c d e f' g h i l rm 

y z n 0 1> q "I' s l vlx 

GH a D c id e f g' h i l'm 

x IY z n 0 "P q r s t v 

IL a b c d e f 8' h i J rm 

v x IY z n 0 p q r s l 

MN a b c d e f g- h "'l l m 

t v .x y z n 0 11> q ~ s 

OP a t> c d e f g' h i l llD 

8 l v x y z n 0 "P q l" 

2R a lb c a e f g b i l !m 

I> s t v x IY z n 0 p q 

a b c d e f g h . l m ST l 

q r s t v ~ ;y z n 0 -p 

vx a b c d e f g n i l m 

p q r s t v .x y z n 0 

YZ a D c d e :f t n 1 1 m 

0 p q r s t v :x y z TI 

Fig. 18. 

papers of Queen Elizabeth's time, it was used for commumcatmg with 

the Enghsh Ambassador to Spam Porta was, m my opm1on, the 

greatest of the old writers on cryptology I also thmk he was one of 

the early but by no means the first cryptanalyst able to solve a system 

of keyed substitution, that IS, where the key is changmg consistently 

as the message undergoes enc1pherment Incidentally, Porta also was 

the inventor of the photographic camera, the progemtor of which was e 

known as the camera obscura 

co~mBEMflAL 36 
REF ID:A62856 

W. F. FRIEDMAN COMF!f>ENJTIAL 

Figure 20 is a picture of what cryptographers usually call the 

Vigenere Square, the Vigenere Table, or the Viger..ere Tableau. It 

co:isists of a set of twenty-six alphabe'"..s in:ccassively d:isplaceC!. one 

letter per row, with the plaint.ext lette!'S at !he 4;()~ of the sqGare, the 

key-letters at the side, anC. the cipher lett.ers !nside. The method of 

using the table is to agree upon a key wol'd, which causes the equivalents of the plaint.ext letters to change as the key 68.nges. Viger..ere 

is commonly credited with having i?ivented th.at sc;:uare and cipher but 

he really didn't and, what's more, never said he did. H!s "table as it 

appears in his book, the first eciition of which was published in 1586, 

is shown in Fig. 21. It is mo!'e complicated than as described in 

ordinary books on cryptology. 

Fig. 19. 

37 CONFIBENTIAL 
REF ID:A62856 CO~~FIBHHIAL INTRODUCTlON 10 CRYPTOLOGY 

Figure 22 I'> one more example of another old official cipher In it 

we can bee the alphabets which could be slid up and down, as a means A 

of changmg the key The "two-square cipher", or "two-alphabet ._ 

cipher" shown m Fig 23 is another of this type It is a facs1m1le of a 

state cipher used m Charles the First's time, m 1627, for C'ommumcatmg with France and Flanders It mvolves coordmates and I want. 

you to notice that there are two complete alphabets inside it, mlended 

to smooth out frequencies The letters of the keywords OPTIMUS 

- -- A B c D E F GB I J K LM N 0 PO R s T u v w x y z 

A a b c d e f f!' h l .1 k 1 m n 0 1> Q 1' s t u v w x y z 

B b c d e f' t h 1 j k lm n O[l> q l' s t u v w x y z a 

c c d e r g h 1 j k 1 m n op q :r s t u v w x .Y z 0 b 

D d e r g' h 1 .i J[ 1 ID1 n op q p s l u v 'W x y z 0 b c 

E e r r n 1 J .It l m n op q r st u v w x !y z Q b cd 

F r g' h 1 j k l m n 0 p q :r s l u v ~ x y z a b cd e 

G If n 1 J k I m n 011> q p s t u v w x y z a 0 cd e f 

H h i j k 1 m D 0 1> q p s l u v IW XIY za 0 c de f g 

I 1 .i k l m D op q rs t u v w x y z a 0 c Cl e r g b 

J J .K I m no p q 1' 8 t u v w x IY z a b c d e r !( h l 

K .k 1 m n 0 "P [q rs t u. v IW :x: y z a b c d e f g h i J 

L l m D 0 p 1q r s t u v IW x y z a o c d. e f 2' b l J k. 

lYl m n 0 'P q I" 8 tu v IW x IY z a b c d e f st b 1. j k l 

•N n 0 l"P q J' 8 tu v w x IY z a b cd e f g h 1 .. i k lm 

.o 0 p lq :r 8 t u v w x ::v z Q b c d c f g' h i j "k 1 m n 'p p q p s t u v w x y z ab c d e r l( h l j 'k 1 m n 0 

0 q :r 8 tu v w x IY z a b c d e f ft b l j .K l tm n 0 Tl 

R p s tu v w x y z a b c d f' f g h i j k l llll no 1> q 

s s l u v w x ly z a b c d e r r n 1 J K J m no p q "[' 

T t u v :w x y z a 0 c d e t 1f h 1. J k lm n op q I' s 

u u v w x y z a 0 c,d e f r h l j k l Im n op q t• s l 

v IV w x :y za 10 c d e r X" 111 l J 1t 1 m n 0 l> q rs t u 

w IW xy z a 0 Cd e f t b l J 1'. l IDl n 0 'p q r s t u v 

x x :.v za b c d e r ~ h i J k 1 m n 0 Ip q r s t u vw 

y IY z a 0 c d e f g h i j k 1 Im D 0 p 1a r s t u v w x 

z z a D c d e r g lh 1 J l.K l m n 0 p Q :r s l u v w .x y 

- - - - --

FJ.g. 20. 

and DOMINUS serve as the coordmates used to represent the letters 

mside the square A thrrd old cipher, one used by George III in 1799 

is shown ID Fig 24 

One wnter deservIDg special attention as a knowledgeable cryptologist ID the 17th Century, and the one with whose cipher I'll close 

this lecture, IS Srr FrancIS Bae.on, who mvented a very useful cipher e 

and mentioned it. for the first time m his Advancement of Leaming, 

co~mBEtHIAL 38 
REF ID:A62856 

\\ F I HI 1'.DMAN cot~ FIBHHh6<L 

publu,,hed 111 1604, m London The de"( npllon 1~ ...,o b1 ief that l 

doubt whether many perc;on~ under~tood wh.1t he wa., drivmg at e But B.1con dcsc..r1bed 1t m full del.ul with example .... , m lu .... gre<ll book 

De Augment1s Scientiarum wluch was published .1lmoA!. 20 yeari:. later, 

m 1{)23, ,md wh1Lh fir1::1t ,1ppe.1red m an Enghc;h tran...,l.:lt1on by Gilbert 

\Vats m 1640 unde1 the title The Advancement of Learning Bawn 

called lu1::1 mvent1on the Hzfrteral Cipher and 1t ii;. '>0 mgemou~ that l 

thmk you should be told about it bO thct.t you will all fully understand 

it 

Fig. 21. 

e. In his De Augrnentis Bacon writes briefly about Ciphers in general 

and says that the VIrtues reqmred m them are three "that they be 

39 COt~FIBEtUIAL 
- - ·- - - - - - - - - - - --· - - - - - - 

REF ID:A62856 

CQMFIBfNflAt INTRODUCTrDN TO CRYPTOLOGY 

easy and not laboriot;.S to write; that they be safe, and impossible to 

be deciphered without the key; and lastly, that they be, if possible, 

such as not to raise suspicion or to ek.tle inquiry." He the.'1. goes on 

to say: "But for avoiding suspicion altogether, I will add en.other 

contrivance, which I devised myself when I was at Paris in my early 

yol:.th, and which I still think worthy of preservation." Mimi you, 

this was 40 years later! Let's consult Bacon for further details. In 

Fig. 25 we see a couple of pages of the Gilbert Wats' translation of 

Bacon's De Augmentis Scientiarum. Bacon shows what he calls "An 

Example of a Bi-literarie Alphabet", that is, one composed of two 

Fig. 22. Fig. 23. 

element.a, which, taken in groupings of :fives, yields 32 permutations. 

You can use these permutations to represent the Jett.era of the alphabet, says Bacon, but you need only 24 of them [because I and J, U and 

V, were th.en used interchangeably]. These permutations of two 

diffment tb.:np..-they may be "a's" and "b's", "l's" and "2's", 

pluses and mi::l~, epples and oranges, ~ything you please- can be a 

used to express or signify messages. Bacon was, in fact, the inventor W 

of the bir.ary cocie which forms the basis of modern electronic digital 

CONFIBEHllAL 40 
REF ID:A62856 

W. P. l'RIEDMAN CONFIBEN'flAL 

computara. Bacon giftB a brief namp]e in tba word 11FUGE"-tbe 

Iatin equivahmt for our modem "SCRAM"-- can be seen :in Fig. 

25. Figure 26 is anotbar uamp]e, which quite obviously isn't what 

it appears to be--a crude picture of a castle, in which tbare are shaded and unpbaded at.ones. It was drawn by a frimd who was a physician and the me=ege conveyed by it is: 

My bw1ain- is to write prescriptions 

And than to 1188 my doses telmn; 

But now I find I spmd my time 

Endeavoring to out-Bacon Bacon. 

41 EONFIBEN'fllcL 
REF ID:A62856 

EOHFIBEt~=flAL INTRODUCTION TO CRYPTOLOGY 

A third example, not quite so obvious, is shown in Fig 27 The 

message conveyed IS Knowledge Is Power* 

So far all this is sunple enough-too much so, Bacon says, for the 

example he used m the case of the word FUGE is patently cryptic and 

would not avoid suspicion under exammation So Bacon goes on to 

descnbe the next step, wluch is to have at hand a "Bi-formed Alphabet", that is, one m which all the letters of the alphabet, both capital 

and small, are represented by two shghtly different forms of letters 

(Fig 28). Having these two different forms at hand, when you want 

to encrpher your secret message you write another external and mnocuous message :five tunes as long as your secret message, using the appropnate two forms of letters to correspond to the "a's" and "b's" repreN..i.:r rs<• rmall 11111ttr rhcr.CJl!w-a-11"'' havr,and 

llllJpcmirm< PorbvrhrsM a\Vayrsopcncd, \Vh~a 

llml may oprdlc and r11"1fie the lntCMIODS of h1s m1nde1 II: 

...,c1r1i..a:u1pba,byWJ.aswluch may be prtfrrued0> 

1be~, and .... ornmudmd ro the..,. prorided thol<ob. 

.,as.,: i:apoblc: of ar:wofold d.m.ntc onc:lv as by llclls by 

Tnimpcu,by Lo!)uundTorch<s,bvth<rq>0rrofM1oka>, 

and any mllrummu. or like nzurc. But to purtuc our cnm 

pr1fc when )'OU addrcflc your rcJfC: to 'A"l'lle 1 trfolvc )"OUr In. 

wucl-1nlokkd Lam 1nr.othis B.-lltmr• Alp/M .Sav the ... 

-u-be 

&..,i.~ 

~ ~ §. £ 

JJu. full. ult..'""· 

Fig. 25. 

* Photo, taken about December 1917, of one of several classes of student offi.-

c.ers detailed by the Adjutant General of the U S Army to pursue a 6-weeks' 

course m cryptology conducted at the Riverbank Laboratories, Geneva, Ilhn01s 

Key to the cipher officers facmg direc.tly forward are "a's," officers facing either 

to left or right are "b's" Begm with first officer m rear row at e.xtreme left 

abaab = K, abbaa = N, etc Civilians seated Colonel Fabyan, (head of the 

Riverbank Laboratories) at left, Mr Friedman (Director of School) at right, A 

Mrs Friedman, the lady m center, other two ladies, secretanes to the Fr1edmans -

-Ed 

(;0.,Ul9DUIAL 42 
REF ID:A62856 

W F FHIEDMAN eor'4flBEr'4=r1~L 

senting your secret message Here's FUGE (Fig 29 ), enciphered 

w1thm an external message saying "Manere te volo donec venero", 

meaning "Stay where you are until I come " In other words, whereas 

the real message says "SCRAM", the phoney one says "Stick around 

awhile, wait for me " Bacon gives a much longer example, ihe 

SPARTAN DISPATCH, here It IS, and here's the secret message 

which it contains (Fig 301 

Fig 27. 

Bacon's bihteral cipher is an extremely ingenious contnvance 

There c.an be no question whatsoever about its authenticity and 

utihty as a vahd cipher Thousands of people have checked hIS long 

example and they all find the same answer --the one that Bacon gives 

43 CONFIBENTIAL 
REF ID:A62856 

co~~FIBEtnlA:L INTRODUCTION TO CRYPTOLOGY 

Fig. 28. 

Figure 31 is a modern example which uses two shghtly different 

fonts of type called Garamond and Imprint, and which are so nearly 

ahke that it takes good eyes to d1fferent1ate them 

The fact that Bacon mvented this cipher and described it in such 

detail lends plaus1b1hty to a theory entertamed by many persons that 

Bacon wrote the Shakespeare Plays and that he inserted secret 

messages m those plays by usmg his cipher If you'd hke to learn 

more about this theory I suggest with some diffidence that you read a 

book entitled The Shakespearean Ciphers Examined I use the word 

diffidence because my wife and I wrote the book which was published 

in late 1957 by the Cambridge Umvers1ty Press 

In the next lecture we'll take up cryptology as used durmg the 

period of the American Revolution by both the Colomal and the A 

British Forces in America • 

CONFIBENTb\L 44 
REF ID:A62856 

W F FRIEDMAN 

1'I OrT•• ADTAllCa111.11T 

Maw ..... _ ............................. fit ......... _ ...................... ......... ---.................... La .. _ ......... x... .......... ..._ 

.......... ,,"'-"-i. 

.ft.11 .?11..i.~1 .. f-. 

.la- fo - G. *1f6lr 

-·· 

Fig. 29. 

COHFIBENTIAL 

Fig. 30. 

ln ali duty or rather piety towards you I satisfy every body except. 

myself. 'MJself I never satzsfy. For so great are the services which J'OU 

have rendered me, that seeing you Jui not rest in your endeavours on my 

behalf tzll the th111g was done, I feel as tf life had lost all zts sweetness, 

because I cannot do as mNCh zn thzs cause of yours.' The occasions are: 

these: Ammonzus the Kmg' s ambassador openl:J beszeges us wzth money • 

the b11S111ess zs car11ed on through the same credttors who were employed 

111 it 11he11 'llOU were here. &c. 

Fig. 31. 

45 COt4FIDEHTIAL 
ce 

I• 

_, i 

... • 

REF ID:A62856 

co~meet11T1At 

Introduction to Cryptology-III 

HY WILLIAM F FRIEDMAN 

Confidential 

The third lecture in this series deals with the cryptosystems employed 

by the British Regulars and by the Colonials during the period of the 

American Revolution This is followed by a brief explanation of the 

cryptanalytic nature of the initial breaks in the solution of the ancient 

Egyptian hieroglyphic writing 

Contmumg with our survey of cryptologic history, the period of 

the American Revolution, m U S history, is naturally of considerable 

mterest to us and warrants more than cursory treatment Information regarding the codes and ciphers employed durmg that period 

has been rather sparse until quite recently, when a book entitled 

Turncoats, Traitors and Heroes by Col John Bakeless, AUS, was 

published m 1959 by Lippincott After a good many years of research Col Bakeless brought together for the first time a considerable 

amount of authentic mformation on the subject, and some of it is incorporated m this lecture 

Accordmg to Col Bakeless--and believe it or not--m early 1775 

the BntISh commander-m-ch1ef m America, General Gage, had no 

code or cipher at all, nor even a staff officer who knew how to compile or devise one, he had to appeal to the commandmg general m 

Canada, from whom he probably obtamed the single substitution 

cipher which was used m 1776 by a Br1tISh secret agent who-agam, 

believe it or not-was General Washmgton's own director-general of 

hospitals, Dr BenJamm Church General Washmgton had means 

for secret commumcation from the very begmning of hostihbes, probably even before the :fightmg began at Lexmgton and Concord If 

the British under General Gage were poorly provided m thIS respect, 

by the time Su Henry Clinton took over from General Howe, who 

succeeded Gage, they were much better off--they had adequate or 

apparently adequate means for secret commumcat10n 

Are you astonished to learn that the systems used by the American 

colonial forces and by the BntISh regulars were almost identical? 

You shouldn't be, because the language and backgrounds of both 

were identical In one case, m fact, they used the same dictionary r• as a code book, somethmg which was almost mev1table because there 

\_ W were so few Enghsh d1ctionar1es available Here's a bst of the systems they used 

41 COMFIBEMfl1'<L 
REF ID:A62856 

COMFIBEl~flAL HISTORY OF CRYPTOLOGY 

a Simple, monoalphabettc substitut10n--easy to use and to 

change 

b Monoalphabet1c substitution with vanants, by the use of a long 

key sentence I'll show you presently an mterestmg example m 

Ben)amm Franklin's system of correspondence with the elder Dumas 

c The V1genere cipher with repeating key 

d Transposition ciphers of simple sorts 

e D1ctionanes employed as codebooks, with and without added 

encipherment Two were specially favored, Entick's New Spelling 

Dictionary, and Bailey's English Dictionary A couple of pages from 

178 ] A C 

Hyp, ., IL re mike mel•1tehol1, fll 41fplrit 

Hypa.'lage:1 ( • cla.1np ef caret,&:,.. 

HJPcr'bolc, f aa ••1ft•ro11on, • d11n1eanoa 

Hyperbo1'u;aJ ••• n.•nw•n1 oreat:eftu1t1n1 

ffypcrloSlua, • ,,....,.,n (reotnn 

liy'pcr, Hypercn1~,/ a cnttc n.a ti.rand 

H7pcrcru'1eal, • cn11col •JOllll afe, fcftre 

lf71>rlm111er f wh1111 """•••lie ltan41rd 

Hi pcr{11'cc6s,f a 1oo•rh of p-• fled! 

II l / ~hen, J ( ) lict•cen wor•• or fyll1blel 

If' pool'ic,L. I med C1 ne cauli1g fth:p 

llypucr..n dri,.,/ OH .it'cOedw11hmet.acflnl1 

H)pochon'dn ... t, IL 111el1ach11t 

ff•poc'11f11 ( dolim111t10n1 I "'"'nee - ffyp'o.ri .. J 1l1ff'rmbl•r111Wl1grne, ftl• 

Hypocrd'1nl, • d111'c111bl1n1, 1nfi1"'"• f11(e 

H711orrir'n1U11 1111 w1rJt••• fircerit•, f•lft 1 

Jh P1••'mc, 1L 1 a •he lower port o( rhe .. 11, 

H>p1•1'• •Ii ,J • -'•llinft f•ltlll·ce, ,..limall'l'J 

H7p lhi'&eal .. conftKur1 .. , ol1ft1nft, perfoH' 

H1pothafi•,/ a c,ft•m upon f•-poliuoia Hy~· 1het'1u1, s. fupDOfed, cond111ooal 

Jlyl) tbirr.' Ci1)y, •t! Up"ll (u .. pofiUO• 

Hy•lt, Hurd 0< Hcrft,/ 1 wood 

Hv•'f r.•f a •l•nl H 1 1 1c1 • trnuhltd •tth fie. 

H)llcr IC•I) 11 ill of •olllcll 

J, 

I P""' m7fclf , J•b bor, ., • "'hlli: ••llr, le challer 

J•b'be er,/ •••who t1lk1 an1n1ell1g1blf 

J1ccnc, ia l71n1 1r: len1dri, 11tendH 

l

oc1n1h, ( a rA, the hJ&<ID•ll 

•ck,/ John, ane11g1ne, fiA lrothrn Hnn 

1clc'al,/ a bo•ft ~•I l1rt1 the hnn'• ,.., ockoJrnr. r .. lnrple .... , ... r.u •• 

•cir. •••P""' {. • 1110nker1 1 coircnmb 

o1Ckbouu1; ~o .. •••"'1 '-,,.., 

JAU 

J••l'daw,/ • ••mmng .,,,. nli 1

tl1 (I W•1ftcoat.,1 flairtrl •t 

ark'padd11r1, f I merrr 1ndrew, I ........ 

•<!•l>Jle,J. a pu11111 o( Jam11 H 

1ftnh1on,/ 1 lnlliPC -•on rcltlrllheli 

oc•l6t1aa, f die .a of rllrowrns or d1rdq 

•di, r • b .. -··· • worthleA llorr. 

dr, • /1 ht ,, .. , -•r, ""' dltWn, llla11 

•dsllr, • •nrul11 •lciDlls, 11nch1ta 

·~•·"' • raa .. cli,/11fftdc1l11...,.•1--" •v.1

11'•1• f a cu11111g la IMllchu 

•'lf•1• • unnen, nllt<W •II,/• pnfan1 •I_. 

··'··· 1ke1,] 1 * • •••'• .... of o5ce, "' . '"""'" • bog..._. . ••· f • ... , .... et &.i1, .... .,. •• r..a 

1m,., • '" cndu "-"• to ..... i• 1111•,f the aprighr polt oh .i1m'b1c,f _.. .......... Illa tons ... alillt r.11 •• 1. 1lrern11llr 

J••'c••,v-. rn ..,•qle,rolleoetotr11• ••'•11r7,/ "Turli•• lol:lttr1 • cuud •n1

ry 11 lhawy, lluttcr•os. llJ• &•••r ,,,,,. • .,, r the llrft 111oerh ortha yen 

•p1n, f 1 1rarndh to wo1k lnc:o1on 

•pan .., • 10 ... .,n., ht •i.ct 6-

1p1n'.irr, f 1 lhoebl1cll, one ••• J•,.,,i 

•r, v " ru d1th, d1f.r!r, d1~ 1 l(VUNI ... r •• , ........... raun4, ... earthc11 •dllrl 

l?l'u"glr, " tr ID conF/luncl1 perplc .. ,.,_ 

.,•son, I s•bfJrrr"', plill'e, aoft<ea• .. ,',n•nt1 J• f•m1ar,f I fli>•H 

,•'per, 1 a prenoa11,.a ftoae ........ , • ,,. .. Dr .... , pib 

>u11'd1ce,f • ••hinper 

1u11'J1ced, tr 111Wted wlrh t!Je j1udla 

aa•t, ., • co ••lit er 1r1Ml •'-•t aunt1/ • r•We,-• .. •ofttlJ 

l!"l!l'...!!J, 

Fig.1. 

the former are shown m Fig 1 To represent a word by code eqwvalent you sun.ply indicated the page number, then whether column 1 

or column 2 contamed the word you wanted, and then the number of 

the word m the column Thus The word "Jacket" would be repre- A 

sented by 178--2-2 • 

f. Small, specially-compiled, alphabetic one-part codes of 600-700 

COMF19EtUIAL 42 
REF ID:A62856 

W F FRIEDMAN eo~mDHHIAL 

items and code names--our old friend the syllabary, or repertory, of 

hoary old age, but m new dress In some cases these were of the 

"one-part" or "alphabetic" type 

g Ordinary books, such as Blackstone's Commentaries on the Laws 

of England, g1vmg the page number, the lme number and the letter 

number m the lme, to bmld up, letter-by-letter, the word to be represented Thus 125-12-17 would md1cate the 17th letter m the 

12th lme on page 125, it might be the letter T 

h Secret mks Both the Br1t1sh and the Americans made extensive use of thIS method 

i Special designs or geometric figures, such as one I'll show you 

presently 

J Various concealment methods, such as usmg hollow quills of 

large feathers or hollowmg out a bullet and msertmg messages written on very thm paper Strictly speakmg, however, this sort of 

strategem doesn't belong to the field of cryptology But it's a good 

dodge, to be used m special cases 

In the way of ciphers a bit more complex than simple monoalphabetic substitution ciphers, the Br1t1sh under Clinton's command used 

a system described by Bakeless m the following terms 

" a substitution cipher m which the alphabet was reversed, 'z' becommg 'a' and 'a' becoming 'z' To destroy frequency clues, the cipher 

changed m each bne of the message, umng 'y' for 'a' m the second lme, 

'x' for 'a' in the thll'd, and so on When the cipher clerk reached 'o' 

m the middle of the alphabet, he started over agam A spy usmg th1S 

cipher did not have to carry mcrimmatmg papers, smce the system was 

eo easy to remember " 

The alphabets of this scheme are simple reversed standard sequences 

ABCDEFGHIKLMNOPQRSTUWXYZ 

ZYXWUTSRQPONMLKIHGFEDCBA 

YXWUTSRQPONMLKIHGFEDCBAZ 

XWUTSRQPONMLKIHGFEDCBAZY 

ONMLKIGHFEDCBAZYXWUTSRQP 

Bakeless doesn't explain why the cipher sequences are only 12 m 

number-nor does the source from which he obtained the mformation, a note found among the Clinton Papers m the Clements Library 

at the UmverSJty of Michigan. 

Bakeless contmues 

"Chnton also used another substitution cipher, with different alphabets for the first, second and third paragraphs Even if an Amencan 

cryptanalyst should break the cipher m one paragraph, he would have 

43 COHFIBEHTIAL 
REF ID:A62856' 

COUFl0Et'4TIAL HrSTORY OF CRYPTOLOGY 

to start all over m the next As late as 1781, however, Sir Henry was 

using one extremely clumsy substitution cipher, m wh1<.h 'a' was 51, 

'd' was 54, 'e', 55 Fmdmg that 'a' was 51 and 'd' was 54, anyone 

could guess !correctly) that 'b' was 52, 'c' 53 Somewhat more complex was his 'pigpen' cipher, m whi<'h twenty-five letters of the alphabet were placed m squares Then an angle alone would represent a 

letter. the same angle with a dot another letter, the same angle with 

two dots still another In some cases, cryptogrdphy was used only for 

a few crucial words m an otherwise 'clear' message, a method also favored by c.ertam American officials " 

Of the first cipher mentioned m the precedmg extract, there JS 

much more to be said Perhaps Bakeless was hm1ted by space considerations In any case; I will leave that story for another time and 

place As for the second cipher Bakeless mentions m the extract, I 

can give you the whole alphabet, for it exists among the Clinton 

Papers 

A B C D E F G H I K L M N 0 P Q R S T U W X Y Z 

51 52 53 54 55 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 

There is no explanation why the sequence begmmng with 50 stops 

with E -55 and then, startmg with F-60 goes straight on without any 

break to Z-78 (Remember that m those days I and J were used 

interchangeably, as were U and VJ , 

Fmally, as to what Bakeless (and others) call the "pigpen" cipher, 

th1S is nothmg but the hoary old so-called "Masonic" cipher based 

upon the 4-Cr!JSS figure 

abtj-+_ a I 

---' b- _J c- __J 

-t---rwhich can accommodate 27 characters, not 25, as Bakeless mdicates 

Letters can be mserted m the design m many different arrangements 

I've mentioned that code or conventional names were used to represent the names of important persons and places m these American 

colonial and Br1t1Sh cryptograms of the Revolution Here are examples selected from a list of code names prepared by the famous 

Bntish spy, Major Andre, chief of mtelhgence under General Clinton. 

For American Generals--the names of the Apostles, for mstance 

General Washmgton was James 

Names of Forts 

Names of C1t1es 

co~mBEt'4TIAL 

General Sullivan was Matthew 

Fort Wyommg - Sodom 

Fort Pitt - Gomorrha 

Ph1ladelph1a - Jerusalem 

Detroit - Alexandria 

44 

-. 

' >; 
REF ID:A62856 

W F. FRIEDMAN 

Names of Rivers and Bays: 

Miscellaneous. 

Susquehanna - Jordan 

Delaware - Red Sea 

Indians - Phar&BeeS 

Congress - Sy1UllJ06Ull 

CONRBENflliL 

I'm sure you've learned as school children all about the treasonable conduct of Benedict Arnold when he was in command of the 

American Forces at West Point; but you probably don't know that 

practically all his exchanges of communications with Sir Henry 

Clinton, Commander of the British Forces in America, were in cipher, 

or in invisible inks. One of Arnold's cipher messages, in which he 

offers to give up West Point for it20,000, is shown in Fig. 2; Fig. 2a 

Fig. la. Fig. lb. 

being the secret version, Fig. 2b, the plain ten. Amold left a few 

words en clair, the ones he considered unimportant; for the important 

ones he used a dictionary as a codebook, indicating the page number, 

column number and line number corresponding to the position in the 

dictionary of the plaint.ext word which the code group represent.a. 

Amold added 7 to these numbers, which account.& for the fact that 

the :first number in a code group is never lees than 8, the central number is always either 8 or 9, and the third number is never lees than 8 

or more than 36. The significant eent.ence appears near the middle 

of the messagie: "If I 198--9-34, 185-8-31 a 197--8--8 •.. " yields the 

plain text: If I point out a plan of cooperation by which S. H. {Sir 

Henry Clinton) shall possess himself of West Point, the Garrison, 

etc., etc., etc., twenty thonunds pound St.erling I think will be a 

cheap purchase for an object of so much importance." The aigna45 CONFIBENflAL 
REF ID:A62856 

COMFIBDHIAL HISTORY OF CRYPTOLOGY 

ture 172-9-19 probably stands for the word "Moor;" Arnold's code A 

name in these commumcations was "John Moore." He had also W 

another name, "Gustavus." 

,,_. I 4 .._, n -""1""- ,,._,..,. ~ .. P 

~,,,,.,. ,.. . .,, ...... ,., _,...,., ,..,,,,,.,. ••7~'' .,.,, ... ,,.,,,,,. 111114 .t. .. 11; '"7, •;- IL~ ,.u ,.. , q __, , •• ., ,~ ~.,h, y 

,.. ,_ ... ~ ,,,_ , :tt Rt' ..., ... 

Fig. 3. 

Figure 3 IS a message m which he gave the Bnt1Sh mformation 

which might have led to the capture of hIS commander-m-chief, 

General Washington Figure 3 at the top shows the code message, 

at the bottom IS the plain text Arnold used the same additive as in 

the precedmg example. W ashmgton, however, was too smart to be 

ambushed-he went by a route other than the one he sa1d he'd take. 

Fig. 4. 

Sir 

W Howe 

1s gone to the 

Cheasapeak bay with 

the greatest part of the 

army I hear he is now 

landed but am not 

certam I am 

left to command 

here with a 

too small force 

to make any effectual 

d1vel'Slon m your favor 

I shall try something cer 

At any rate It may he of use 

to you I own to you I thmk 

gr W's move Just at thJS time 

the worst he could take 

much JOY on your success 

You may find Fig 4 mterestmg as an example of the special sort 

of mask or grille used by Arnold_ and by the British m their negotiaCONFIBDHl>'<L 46 
REF ID:A62856 

W F FRIEDMAN CO~UIBEtUIAL 

tions with hun The real or significant text IS written m Imes outlmed by an hour-glass figure and then dwnmy words are supplied to 

fill up the lines so that the entire letter apparently makes good 

sense. To read the secret message, you're supposed to have the 

same size hour-glass figure that was used to conceal the secret message In Fig 4 the left-hand portion shows the "phoney" message 

Masks havmg small rectangular apertures were also used, the significant words bemg wntten so that they were disclosed when the mask 

was placed on the written message so as to isolate them from the 

non-significant words The significant text in this example is shown 

ID prmted form to the right of the original hour-glass design 

Arnold even used the tnck, mentioned above in method J, that was 

quite similar to one used recently by the 

Russian spy, Colonel Abel (Fig. 5) who 

was arrested m New York m June 1957, 

tned and convicted, and 1s still languIShmg ID a Federal prISon. 

An mterest1Dg epISOde mvolvmg concealment of thlS sort 1s recorded by 

Bakeless. An urgent message from Sir 

Henry Clinton, dated 8 October 1777, 

and written on thin stlk, was concealed 

m an oval silver ball, about the size of a 

Fig. 5. ri:O.e bullet, which was handed to Daniel 

Taylor, a young officer who had been promised promotion If he got 

through ahve. The bullet was made of silver, so that the spy could 

swallow it without mJury from corrosion Almost as soon as he 

started, Taylor was captured Reahzmg hlS peril too late, the spy 

fell mto a paroxysm of terror and, crymg, "I am lost," swallowed the 

stlver bullet Admm1strat10n of a strong emetic soon produced the 

bullet with fatal results, for Taylor was executed "A rather heartless American joke went around," adds Bakeless, "that Taylor had 

been condemned 'out of hlS own mouth'." 

We next see (Fig. 6) one Benedict Arnold message that never was 

deciphered It is often referred to as "Benedict Arnold's Treasonable 

Cow Letter." Only one example lS extant, certam words have purely 

arbitrary meanmgs, as prearranged The letter was written JUSt 

two weeks before the capture of MaJor Andre 

In Fig 7, we see a British <..'lpher message of the vmtage 1781 It 

was deciphered before finding the key, always a neat trick when or 1f 

you can do it The key--the title page of the then current British 

47 CO~IFIBEM'ffAt 
CO~IFl9EtiUIAL 

COHFlf>ENflAL 

REF ID:A62856 

HISTORY 01'' CRYPTOLOGY 

./L.. ~~ _, _ __, .:../ 

t:-~,..i...-"'~ ... .i: _,,,,,,_ 

"--'I'• -/.----,-Atl/:,..r;.:.,...,_.,J 

• ~, '-'"'"I'-·" "_,_ ·~'-"""-- 4-

.c. ~"-JI' JI,,,_ - ·"'-"'7 ·- sl.-..17 ,,,, •• / 

~·"--~- ~-- ~ ,,,;:..""_ ... -·"··" ~ Z-;111-.6?,-'~ /~._,,,a_ 

.-7 ~;- 11 7.--•-"-r·.,~ " c 6 c ( "'7',,,, ;kt'_ ,,. ,, ___ I. ~ A< 

,;:,.. -.;> ""3.-. ... ~~ . .,,. •• /.if .... _. 

~~--·I/A 7J--i-,,.-,-~ .. 

~ ,,._.,,_? ?-'"/"..-..-

./-

,,,~_ ,I ,_ 

r- ~ .. ::.12'A. .. 

~L~ AA--"A 

·7 c:::.~::_,,/ 

Fig. 6. 

11111 • -~ 11'M111 Id II 

Fig. 7. 

48 
REF ID:A62856 

W F FRIEDMAN CONFIBENTIAL 

Army List -1s shown m Fig 8 The numbers m the cipher text 

obviously refer to hne numbers and letter numbers m the lme of a 

key text, the first ber1es of numbers, viz., 22 6 7 39 5 9 17, md1catmg 

hne number 22, letter numbers 6 7 39 5 9 17 m that hne Because of 

so many repetitions, the plain text was obtamed by straightforward 

analysis by an officer recently on duty m NSA, Captam Edward W 

Knepper, USN, to whom I am mdebted for this mterestmg example 

The plam text, once obtamed, gave hun clues as to what the key text 

might be, sunply by placmg the plamtext letters m their numencaleqmvalent order m the putative key text ThIS done, Captain 

Knepper was quick to reahze what the key text was-a Br1t1Sh Army 

List The date of the message enabled hnn to fmd the hst without 

much difficulty m the Library of Congress (Fig 8) 

lw P1•1111u10.., cJ1hl Klei 'T lf'l"luLRo\llL• 

The S r: < R 1 T A 11 ' at W A R 

A 

L I s T 

o• THt. 

GENERAL and I !LLD OFi'iCERS, 

As 1hC"y rn1S. 1n chi: Anny. 

,,. I Ill' 

orricERS on 11 .. hml REGl\1EN'TS 

". 

HORSE, DRAGOON'S, and FOOT, 

u .. TllP 

BRIT!•H ond IRhH l:STABLISll\1Ei..Ts 

(la.ti h ...... .. 

A• A.1.•Hit.alT"-AL l11n11) 

1'I Jl•,al IH••••T Df Air .1.111r alld L•P' SI.& •• ,. ... _, 

... 1111• An1LLUI' ... 1••1•1111 

A• •hf MA.11 1 h "" Pl.LL ... II.ALP PAY 

• IT 11 

ThtD•tnof thc1r(.o 011u1on1 uthey rank 1nach. 

I! on pe .. .i '" 11>< •••ti T• a ........ Lnul .. HT c ........ llL "' ... •AJllTI. 

G1H11••• • H-111 A ..... -•1Wr A•L••••c .. 

an1•01r1L11•••Hu' p,.., A .. 

A SUCCESblON of COLO.NELS, Widll diil u ....... ••II l1e1llH'P '-.. .., OHll .. 

CL•'P•1H •r 

MDCCLXXVIII 

LONOON 

== - ......... J K11.LH1•1.-~4*ir-"1"D#• .. ,.,,. ... 'L 

Fig. 8 

There was an Amencan who seems to have been the Revolution's 

one-man N abonal Secunty Agency, for he was the one and only 

cryptologic expert Congress had, and, 1t IS clarmed, he managed to 

deCipher nearly all, if not all, of the BntJ.Sh code messages obtained 

m one way or another by the Amencans Of course, the chief way 

m which enemy messages could be obtained m those days was to 

capture couriers, knock them out or knock them off, and take the 

49 
REF ID:A62856 

<;OMF19EMTIAL HISTORY OF CRYPTOLOGY 

messages from them ThJS was very rough stuff, compared to gettmg the matenal by radio mtercept, as we do nowadays e 

I thmk you'll be mterested to hear a bit more about that one-man 

NSA His name was James Lovell and besides bemg a self-tramed 

cryptologist, he was also a member of the Contmental Congress. 

There's on record a very mterestmg letter which he wrote to General 

Nathaniel Greene, with a copy to General Washmgton Here it IS 

Pluladelplna, Sept 21, 1781 

Sll' 

You once sent some papers to Congress which no one about you 

could decyP.her Should such be the Case with some you have lately 

forwarded I presume that the Result of my pains, here sent, will be 

useful to you I took the Papers out of Congress, and I do not thmk 

it necessary to let it be known here what my success has been in the 

attempt For it appears to me that the Enemy make only such Changes 

in their Cypher, when they meet with mISfortune, as makes a difference of Position only to the same Alphabet, and therefore if no talk of 

OISCovery IS made by us here or by your Family, you may be m Chance 

to draw Benefit thlS Campaign from my last Night's Watching 

I am Sir with much respect, 

Your Friend, 

JAMES LOVELL 

MaJ Genl Greene A 

<With copy to Genl Washmgton) WI' 

In tellmg you about Lovell I should add to my account of that 

mterestmg era m cryptologic history an episode I learned about only 

recently When a certam message of one of the generals m command of a rather large force of Colomals came mto Clinton's possession he sent it off post haste to London for solution Of course, 

Clmton knew it was gomg to take a lot of time for the message to get 

to London, be solved and returned to Amenca-and he was naturally a bit rmpatient He felt he couldn't afford to wait that long 

Now it happened that m his command there were a couple of officers 

who fanCied themselves to be cryptologists and they undertook to 

solve the message, a copy of which had been made before sendmg the 

ongmal off to London Well, they gave Sir Henry their solution 

and he acted upon it The operation turned out to be a dismal 

failure, because the solution of the would-be-cryptanalysts happened 

to be quite wrong' The record doesn't say what Clinton did to 

those two unfortunate cryptologists when the correct solution arrived from London some weeks later By the way, you may be 

mterested m leammg that the BntISh operated a regularly-established 

cryptanalytic bureau as early as In the year 1630 and It contmued e 

to operate until the end of July 1844 Then there was no such 

estabhshment until World War I I WISh there were trme to tell 

COt~FIBEt'4'flAL 50 
REF ID:A62856 

W F FRIEDMAN EOHF16~1'4'f'IAL 

you some of the details of that fascmatmg and httle known bit of 

Bntish history 

There's also an episode I learned about only very recently, which 

is so amusing I ought to share it with you It seems that a certam 

Bntish secret agent m America was sent a message m plam Enghsh, 

givmg hun mstructions from his superior But the poor fellow was 

illiterate and there wasn't anythmg to do but call upon the good 

offices of a friend to read it to him He found such a friend, who 

read him lns instructions What he didn't know, however, was that 

the friend who'd helped him was one of General Washington's secret 

agents' 

The next illustration (Fig 9) is a picture of one of several syl-

.K ... .., ... ,.,..,, ,.., .. 14t ...... 4f.I /..~I ... 

ry ..... 

,.,. . ,., 

.. , ...... "'" .. ,., ... ~. 

. -- "" I ""'"""' ... ...,......_ ..., • t-t- ... , , ........ 1'8)' - ~· ~,. 

:::? .. , "'"-A. ,,. .,... ... , ~ 911' .l..-.. ~, ,... ,,. .,._ I.•& '4- • ., : l~t 

.....,,,_.,. S.t'J ,._. .... ... ,..,_ :z ~ ..,, - ... ,,,.. 1-, '" ·- _..,. I.JI' 

- .. , - ,.. ., ........,1•• .... , .. ~ .... ~ ~· .. .... ~ "' 

.,, ' ,,,..,._ "' ... -- .1•1 

..,, ''t J- . .,,, ... ... , .... ..,...,." .~~ r>' - !~~ ·- . ., .,._ s•• ~ ~ft ·- IU --

_.... .... - .,, ,.. .. J71 ,,., -- ... , - ... ..,._ ·- .,. ... ,._ ... .,,.~ ... :J ,,,. .,.,. 4~7 

- •v - >olo ·~ "'1 - l'r,.l 

..... .... .11 'it . .. '•"" ~;~I ht" r'>• ' 

---....... •1• '"' ·- "" ,,.,, ' ... -- J ,. ..... a.... , ..... _._ .., - _,, ?& ..... "'" .... u., - ,,, u ... ,. . ,,,,_ , .. _ .. ru 

- ... ... _ .,. .....,, .... M. I '°II ' ........ U/ 

Fig. Ba. 

Fig. Bb. 

51 COHFIBEtHl>*cL 
REF ID:A62856 

. EOt~FIBEt~flAL HISTORY OF CRYPTOLOGY 

labar1es used by Thomas Jefferson It IS constructed on the so-called 

two-part prmc1ple, which was explamed m the precedmg lecture Fig 

9a 1s a portion of the encodmg sect10n, and Fig 9b 1s a portion of the 

decodmg section, m which the code eqmvalents are m numerical order 

accompanied by their meanmgs as assigned them m the encodmg 

section This sort of system, which, as I've already explamed, was 

quite popular m Coloma! times as m the early days of Italian cryptography, is still m extensive use m some parts of the world 

A few mmutes ago I mentioned BenJamm Franklm's cipher system, 

which, if used today, would be difficult to solve, especially if there 

were only a small amount of traffic m 1t Let me show you what it was 

Franklm took a rather lengthy passage from some book m French 

and numbered the letters successively These numbers then became 

equivalents for the same letters m a message to be sent Because the 

key passage was m good French, naturally there were many variants 

for the letter E-m fact, there were as many as one would expect m 

normal plam-text French, the same applied to the other high-frequency letters such as R, N, S, I, etc What thIS means, of course, 

is that the high-frequency letters m the plam text of any message to 

be enciphered could be represented by many different numbers and 

a solution on the basIS of frequency and repetitions would be very 

much hampered by the presence of many variant values for the same 

plamtext letter In Fig 10 you can see this very clearly 

IY ... ..... ... " ... .. , ., J' ' 

. ,. ... ... ,. '" ·' ..,., ... .. 311:1.1 

.. ." IPM .... ...... . .... 3C1 I 

I' .... 'llJ ..... .,,, JH I 3•: ' 

,, '°' ..... '111 If ...,, JIJ I 1•J •.c ,. J ,,. ,( ... ,. ... ,. Jlf • '. .... ... , '"l ... ') Ill I" J"• I i: ~ nl' .,.., 

.,, . •••• 316 / •n•• -.. • 74 ' ..... . .. , 1•1 •• IJI I JM• I 

fl I •JP" tn IN •'s •••• .. ,, .1"!11t 7' .. ..... 140 .. "'° ,, 321-1,, 3.., I .. "' 77, ...... .. 117.J , 71 •• lfl, 11~. 3¥> I 

Ip# IOf'" .... 131 ' ... " " . d.2 • .. f 3~· , 

•11: lo, ..... ..., ' I.I• • 3•• ,. 1; ..... 179 It .... ... ., 17i UJ ' ,· l»J J 

he ... , H4 II 

•4' ..,, 171, / ;~ ... •• !) '· us ,( 3•• I 147 • llO .. 111.1 ' . 96 ... 

Fig. 10. 

I know of but one case m all our U S history m which a resolution 

of Congress was put out m cryptographic form. It IS shown m Fig. 11 

-a resolution of the Revolutionary Congress dated 8 February 1782 

I have m my collection not only a copy of the resolution but also a 

copy of the syllabary by which it can be deciphered 

Interest m cryptology m America seems to have died with the 

EOt~FIBENflAL 52 
REF ID:A62856 

W. F FRIEDMAN 

.IJ.-... ~r- ._ J., ~~,.._ ....... , . , ... )J,.~ .. f,,,.,., .. .. 

·-J. ~:ii.'" I« ...... '-4! .. :: ... 1;._..L_/-.. _,, .. _ .. :t._,_ ~-...3 -

.,__1~~~ ~ •-=-_~ .. .,.,.-*':-!= ~H·h~u: __!,., .. _. 

..... -~-·; "'#Iii---.. ,._ - --- .. ·-·--~- ,_ r..,..-4'-- .c-_11. _.,. -- '-" - ~·- ,....,,, 9W .11• r ' -•--1-:-~-~~ .:-.. ;. - I" 

- ..... •7 ........ .1u _,..~.-.._._ •- • " cf ·• ~- ..... .,_/'---.C~ -~-It" - """' 

., ' I .. ; C ,. 

'\::.. • !A hf - •r.. •••II' -: ~r-L. r 

-7•-<- ..... wt--.. ·-'· - - - -·., - -

cu ... .... , .. -- .. , ~ w ..... ,. .. ,.., iff/f. - '1.·- - ·-...:..... .,.. "_:_. -

~ - 6 - <!"+• 

.,,_~,.... 1 ·~ 

....... ~- - "''!( '!"- .z_ ....... - -':-1"1 - ~ ... ..;_ ~&.... ·- ~ - ,.. .. ;- .. ..,. ... ,,; - -' - ... .c. .... - ~.. •-I ... -#!,,__._ '" 

'%/I.- •• .r.i..,... ;r _,, .... ......, 

I - - •Ao• I"" -,.. .. -T - •-Jf - ... ,S I 

"!" - ~.., ~·- ..... '":- '!::!_!_--=-.:/.!·~ - __ -..... -;-~ 

. :- - ........ ,,.~ "' ~~ - ~-·'·~-Jb -- ..... - .... ..,,._ ?'.- - - .. - 4.,,,., I tM- .... I~ -, ••-< --- ... ~.., 

&or -- 'to. - - ... ...,ag - t~• -- __, - - --- "" "" "" I 

Fts.11. 

CONFIBEHTIAL 

passing of Jefferson and Frankhn. But if interest in cryptology in 

America wasn't very great, Jf it existed at all after the Revolution, 

this was not the case in Europe. Books on the subject were written, 

not by professionals, perhaps, but by learned amateurs, and I think 

you will find some of them in the NSA library if you're mterested in 

the history of the science. The next illustration (Fig. 12) is the fron" 

tispiece of a French book the title of which (translated) is "Counter" 

espionage, or keys for all secret communications." It was published 

in Paris in 1798. In the picture, we see Dr. Cryppy himself, and 

perhaps a breadboard model of a GS-11 research analyst, or maybe 

an early model of a WAC. 

I am now going to tell you something about the early steps in find" 

ing an answer to the BP"Old mystery presented by Egyptian hiero· 

glyphics, not only because I think that the solution represents the 

nut landmark in the history of cryptology, but also because the 

story is of general interest to any aspiring cryptologist. About 1821 

a Frenchman, Champollion, startled the world by beginning to publish translations of Egyptian hieroglyphics, although in the budding 

new field of Egyptology much had already transpired and been pubpublished. In Fig. 18 we see the gentleman and in Fig. 14, a picture 

of the great Napoleonic :find that certainly facilitat.ed and perhaps 

made possible the solution of the Egyptian hieroglyphic writing-the 

Rosetta Stone. The Rosetta Stone was found in 1799 at Rashid, or, 

58 CONFIBCN'fl:AL 
REF ID:A62856 

COMFIBEt~TIAL HISTORY QI<' CRYPTOLOGY 

Fig. 12. 

as the Europeans call 1t, Rosetta, a town m northern Egypt on the 

west bank of the Rosetta branch of the N 1le Rosetta was in the 

v1cm1ty of Napoleon's operations which ended m disaster When the 

peace treaty was written, Article 16 of it required that the Rosetta 

Stone, the significance of which was quickly understood by both the 

conquered French and v1ctor1ous Bntish commanders, be shipped to 

London, together with certam other large antiquities The Rosetta 

Stone still occupies a prominent place m the important ex1ub1ts at 

the Br1t1sh Museum The Rosetta Stone is a b1-lmgual inscription, 

because it IS m Egyptian and also Greek The Egyptian portion 

consists of two parts, the upper one m h1eroglyph1c form, the lower 

Fig. 13. 

CONFIBEtHIAL 54 
REF ID:A62856 

W F FRIEDMAN COt~FIBet'llflAL 

one m a sort of cursive script, also Egyptian but called "Demotic " 

It was soon reahzed that all three text.s were supposed to say the 

same thmg, of course, and smce the Greek could easily be read, it 

served as somethmg called m cryptanalysIS a "crib." Any time you 

are lucky enough to find a crib 1t saves you hours of work It was by 

means of this ,bi-lingual inscription that the Egyptian h1eroglyph1c 

Fig. 14. 

55 <;ONA9EN'Fh\L 
REF ID:A62856 

EOt~FIBHfflAL HISTORY OF CRYPTOLOGY 

wr1tmg was finally solved, a feat wluch represented the ~uccessful 

solution to a problem the maJor part of which was hngmstJc m char- e 

acter The cryptanalytic part of the task was relatively sunple 

Nevertheless, I thmk that anyone who aspires to become a professional cryptologist should have some idea as to what that cryptanalytic feat was, a feat which some professor (but not of cryptologic 

science I thmk it was Professor Norbert Wiener, of the Massachusetts Institute of Technology) said was the greatest cryptanalytic 

feat m history We shaJI see how wrong the good professor was, because I'm going to demonstrate JUSt what the feat really amounted 

to by showmg you some simple pictures 

Frrst, let me remmd you that the Greek text served as an excellent 

crib for the solution of both Egyptian texts, the hieroglyphic and the 

Demotic, the latter merely bemg the conventional abbreviated and 

modified form of the Hieratic character or cursive form of h1eroglyph1c wntmg that was m use m the Ptolemaic Period 

The imtial ~tep was taken by a Revere_nd Stephen Weston who 

made a translation of the Greek inscription, which he read m a paper 

delivered before the London Society of Antiquaries, m April 1802 

In 1818 Dr Thomas Young, the phys1c1st who first proposed the A 

wave theory of hght, compiled for the 4th volume of Encyclopaedia • 

Britannica, published m 1819, the r0!!ults of his studies on the Rosetta Stone and among them there was a hst of several Egyptian 

characters to which, m most cases, he had assigned correct phonetic 

values He was the first to grasp the ulea of a phonetic principle in the 

Egyptian hieroglyphs and he was the first to apply it to their decipherment He also proved something which others had only suspected, 

namely, that the hieroglyphs m ovals or cartouches were royal names 

But Young's name is not associated m the pubhc mmd with the 

decipherment of Egyptian hieroglyphics-that of Champolhon is 

very much so Yet much of what Champolhon did was based upon 

Young's work Perhaps the greatest credit should go to Champollion 

for recognizing the major importance of an ancient language known as 

Coptic as a bndge that could lead to the decipherment of the Egyptian 

h1eroglyph1cs As a lad of seven he'd made up his mind that he'd 

solve the hieroglyphic wntmg and m the early years of the 19th 

Century he began to study Coptic In his studies of the Rosetta 

Stone his knowledge of Coptic, a language the knowledge of which had 

never been lost, enabled him to deduce the phonetic value of many 

syllabic signs, and to assign correct readmgs to many pictorial characters, the meamngs of which became known to him from the Greek A 

text on the Stone 9 

The followmg step-by-step account of the solution is taken from I 

COMFl9Et~fl~L 56 
REF ID:A62856 

W F FRIEDMAN 

d httle brochure entitled The Rossetta Stone, pubhshed by the Trustees 

of the British Museum It was written m 1922 by E A Walhs 

Budge and was revised m 1950 I quote 

"The method by wh1rh the greater part of the Egyptian alphabet. 

was recovered 1s this It was assumed correctly that oval~ , 

or "cartouche" as it is called, always contamed a royal name There 

is only one cartouche (repeated six times with shght modrfications) 

on the Rosetta Stone, and this was assumed to cont.am the name of 

Ptolemy, because it was certam from the Greek text that the mscr1pt1on concerned a Ptolemy It was also assumed that if the 

cartouche did contam the name of Ptolemy, the characters m 1t 

would have the sounds of the Greek letters, and that all together 

they would represent the Greek form of the name of Ptolemy Now 

on the obehsk which a certain Mr Banks had brought from Ph1lae 

there was also an inscnption m two languages, Egyptian and Greek 

In the Greek portion of 1t two royal names are ment10ned, that IS 

to say, Ptolemy and Cleopatra, and on the second face of the obelISk 

there are two cartouches, which occur close together, and are filled 

with hieroglyphs which, 1t was assumed, formed the Egyptian eqmvalents of these names When these cartouches were compared with 

the cartouche on the Rosetta Stone 1t was found that one of them 

contamed h1eroglyph1c characters that were almost 1dent1cal with 

those which filled the cartouche on the Rosetta Stone Thus there 

was good reason to behave that the cartouche on the Rosetta Stone 

contamed the name of Ptolemy written m h1eroglyph1c characters 

The forms of the cartouches are as follows 

On the Rosetta Stone - (-~-==-~-~ -r 1'-~3-~ -J -~ -~~] 

On the Obehsk from Ph1lae - ( ~ f1 ~ ~~ r f 3 ~ l :e=i:] 

In the second of these cartouches a smgle sign takes the place of 

three signs at the end of the first cartouche Now it has already 

been said that the name of Cleopatra was found m Greek on the 

Ph1lae Obehsk, and the cartouche which was assumed to contam 

the Egyptian eqmvalent to this name appears m this form 

(~~flo~~~~J Takmg the cartouches which were supposed to contam the names of 

Ptolemy and Cleopatra from the Phdae Obelisk, and numbermg the 

signs we have 

Ptolemy, A d 6 af1_&~s~~1rsf•~ ,2Lg.g 1aJ ~] 

Cleopatra, B 

57 COt4'FIBEt4'flAL 
REF ID:A62856 

co~menn1~L HISTORY OF CRYPTOLOGY 

Now we see at a glance that No 1 m A and No 5 m B are identical, 

and JUdgmg only by their position m the names they must represent e 

the letter P No 4 m A and No 2 m Bare identical, and argumg as 

before from their position, they must represent the letter L As L 

is the second letter m the name of Cleopatra, sign No 1 m B must 

represent K In the cartouche of Cleopatra, we now know the values 

of Signs Nos 1, 2 and 5, so we may write them down thus 

( K L 3~ •f1 P e~ c:b. ~ 9~ :~~] 

In the Greek form of the name of Cleopatra there are two vowels 

between the L and the P, and m the hieroglyphic form there are 

two hieroglyphs, this Q and thIS f( , so we may assume that 

the first is E and the other 0 In some forms of the cartouche of 

Cleopatra, No 7 (the hand) is replaced by a half Circle, which is 

identical with No 2 m A and No 10 m B As T follows P m the 

name Ptolemy, and as there 1s a T m the Greek form of the name of 

Cleopatra, we may assume that the half circle and the hand have 

substantially the same sound, and that that sound is T In the Greek 

form of the name Cleopatra there are two A's, the pos1t10n of which 

agree with No 6 and No 9, and we may assume that the bird has the 

value of A Substitutmg these values for the hieroglyphs m B we 

may write it thus 

C H JO 11~ K L B 0 P A T <::> A ~ !;)~ 

Thomas Young noticed that the two signs c and C) always followed 

the name of a goddess, or queen, or pnncess Other early decipherers 

regarded the two signs as a mere femmme termination The only 

sign for which we have no phonetic eqmvalent is No 8, the lens, and 

it IS obvious that this must represent R Insertmg thIS value m the 

cartouche we have the name Cleopatra deciphered Applymg now 

the values which we have learned from the cartouche of Cleopatra 

to the cartouche of Ptolemy, we may write it thus 

(r To L~e~~1rsf~"'-, :,,r T 1af~) 

We now see that the cartouche must be that of Ptolemy, but it is 

also clear that there must be contained m it many other hieroglyphs 

which do not form part of his name Other forms of the cartouche of 

Ptolemy are found, even on the stone, the simplest of them written 

thus 

COHFIBEtUIAL 58 
REF ID:A62856 

W l• FRIEDMAN COt~FIBEtHIAL 

It was therefore evident that these other signs if .,_ 10 11,1a J 1c a • I o a o 13 •-• 

- were royal titles corresponding to those found m the Greek text on 

the Rosetta Stone meamng "ever-hvmg, beloved of Ptah" Now the 

Greek form of the name Ptolemy, i e Ptolema1os, ends with S We 

may assume therefore that the last s1gnr m the simplest form of the 

cartouche given above has the phonetic value of S The only hieroglyphs now doubtful are c::. and Q 9 , and their position in the 

name of Ptolemy suggests that their phonetic values must be M and 

some vowel sound in which the I sound predominates These values, 

which were arnved at by guessing and deduction, were apphed by 

the early decipherers to other cartouches, e g 

Now, in No 1, we can at once write down the values of all the signs, 

viz , P I L A T R A , which is obviously the Greek name Philotera 

In No 2 we know only some of the hieroglyphs, and we write the 

cartouche thus 

(A L-.::::A s ~-Ta-) 

It was known that the runmng-water sign NW1Moccurs in the name 

Beremce, and that it represents N, and that thIS sign -++- is the 

last word of the transcnpt of the Greek title "Kaisaros," and therefore represents some S sound Some of the forms of the cartouche of 

Cleopatra begin with (~l. and it IS clear that its phonetic value 

must be K Inserting these values in the cartouche above we have 

c A L K S ~ N T R s) 

which is clearly meant to represent the name "Alexandros," or 

Alexander The position of this sign (q ) shows that it represented 

some sound of E or A 

Well, I've showed you enough to make fairly clear what the problem was and how it was solved As you may already have gathered, 

the cryptanalysis was of a very simple vanety 

The grammar?-Well, that's an entirely ddferent story: There's 

where the difficult part lay It was very fortunate that the first 

attacks on Egyptian hieroglyphics duin't have to deal with enciphered writing Yes, the Egyptians also used cryptography; yes, 

there are "cryptographic hieroglyphics'" We'll get to these later, 

but at thIS point it may be of interest to many of you to learn somethmg about what the Rosetta Stone had to say, as set forth by Dr 

Budge 

59 CONFIBENHAL 
REF ID:A62B56 

COl~FIBEt~fl7'tl HISTORY OF CRYPTOLOGY 

Fig. 15-A. 

co~~FIBEt'4'fli'8\L 60 
REF ID:A62856 

W F FRIEDMAN 

Fig.15-B. 

61 

- - --------

COr-IFlf'JEl~flAL 

COMFIBEHTIAL 
COt~FIBEHllAL 

REF ID:A62856 

HISTORY 01<' CRYPTOJ.OGY 

"The opening Imes are hllcd with a Ju,,t of the titles of Ptolemy V, 

and a series ol epithets wluch proclaim the king's piety towards the 

gods, and his love for the ggyptians and hlS country In the second A 

section of the inscription the priests enumerate the benefits whu.h he W 

had conferred upon Egypt, and whKh may be thus summarized 

1 Gifts of money and corn to the temples 

2 Gifts of endowments to temples 

3 Rem1S1:11on of taxt!S due to the Crown 

4 Forgn.eness of debts owed by the people to the Crown 

7 Reduction of tees payable by t,and1dates for the priesthood 

8 Redut,tlon of the dues payable by the temples to the Crown 

13 Forgiveness of the debts owed by the priests to the Crown 

14 Redut,tJon of the tax on byssus (a kmd of flax or cotton fibre) 

15 Redut,bon of the tax on corn lands 

Could it be that msta.llment-plan buymg was rampant m Ancient 

Egypt too, so that people didn't have enough left to pay their 

taxes? 

Now, let's go back to those cryptographic hieroglyphics mentioned 

a moment ago Here, m Fig 15-A for msta.nce, 1s a picture of an 

inscription on a stela now m the Louvre, m Pans Lmes 6-10, 

mclusive, below the seated :figures under the arch, contam secret 

writmg m hieroglyphics, m Fig 15-B, these Imes are seen enlarged I 

won't attempt to explam the nature of the cryptography mvolved 

It's pretty simple-something hke the sort of cryptography mvolved m 

our own type of rebuses, and m our modern acronymic abbreviations, such as CARE, which stands for Cooperative (for J American 

Rehef Everywhere, or NASA, for the National Aeronautics (and) 

Space Admimstration Just to show you a bit of the cryptography 

that Dnoton presents, without undertakmg to explam what is mvolved, m Fig 15-C can be seen m sequence 34 hieroglyph~c characters which are m Imes 1, 2 and part of 3, of Fig 15--B (the 6th, 

7th, and part of the 8th Imes of Fig 15-A) 

The followmg extracts, translated from a long article by Prof. 

Etienne Drioton m "Revue D'Egyptologie," Pans, 1933, will be of 

mterest· 

(P 1) "From the time of the Middle Empire onwards, Egypt 

had, alongside the official and normal system of wntmg, a tradition of cryptographic writing, the oldest known examples of which 

are to be found m the tombs of Beni-Hassan, and the most recent 

m the mscnptions of the temples of the Greco-Roman epoch 

* * * * * * * 

(P 32) It is necessary to add to the enumeration of the crypto- A 

graplnc procedures the variation m the appearance of the crypto- W 

graphic signs themselves This vanation, without however 

EOt~Fl9ENflAL 62 
·e 

REF ID:A62856 

W 1" J.<'H.IEDMAN C:Ol'4flf>El'4TIAL 

affecting their value, can (1) modify the appearance of the signs, 

(2) affect their position m vanous ways, and (3) combine these 

signs with others Finally, to note a last pecuhanty of 

these 1nscnptions which, because of their fine form, deserve to be 

considered the classics of the cryptography of this period, the 

scribe has several times successfully carried out m them what was 

doubtless considered to be the trmmph of the genre the groupmg 

of signs which offer a possible but fallacious meamng m clear, 

alongside a cryptographic meanmg which IS the only true one " 

* * * * * * * 

And now for the most mtr1gumg explanation offered by Dr1oton 

as to why cryptography was mcorporated m these mscr1pt1ons You 

know qmte well why cryptography IS employed m military, diplomatic, bankmg, and mdustrial affairs, you also know perhaps that 1t is 

used for other purposes, m love affairs, for example, and m 1lhCit 

enterprises of all sorts, and you probably also know that it is often 

used for purposes of amusement and d1vers1on, m tales of mystery, 

m the sorts of thmgs published m newspapers and hterary JOurnalsthey are called "crypts" But none of these explanations will do for 

the employment of cryptography m Egyptian h1eroglyph1cs Here's 

what Dr10ton thmks 

(P 50 l "There remains, therefore, the suppos1t1on that, far 

from seekmg to prevent readmg, the cryptography m certain passages of these inscriptions was mt.ended to encourage their reading 

The appeals which often introduce formulae of this type, and 

which are addressed to all VIS1tors to the tombs, show m fact how 

much the Egyptians desired to have them read, but also, by the 

very fact of their existence, what an obstacle they encountered in 

the indifference, not to say satiety, produced by the repetition 

and the monotony of these formulae To attempt to overcome 

thIS md1:fference by offenng a text whose appearance would pique 

cur10s1ty, based on the love, traditional m Egypt, for puzzles, to 

get people to deCipher, with great difficulty, what was desired they 

should read, such is perhaps, m last analysis, the reason why the 

three monuments of the per10d of Amenoph1s III here consJdered 

present certain passages m cryptography 

One must suppose, m this case, that the goal was not attained 

and that it was very quickly seen that the expedient produced, on 

the apathy of the v1s1tors, an effect opposite to that mt.ended it 

removed even the shghtest desire to read the mscnptions presented 

m this form The new procedure was therefore, - the monuments seem to prove it -, abandoned as soon as it had been tried." 

* .. * * * * * 

63 EOt~FIBEtnlAL 
REF ID:A62856 

eor~flf)!l~TIAL HISTOH.Y OF CRYPTOLOGY 

Before leavmg the story of Champolhon's mastery of Egyptian 

hieroglyphic writmg, I thmk I should re-enact for you as best I can 

m words what he did when he felt he'd really reac.hed the solution 

to the mystery I'll preface it by recalling to you what Archimedes is 

alleged to have done when he solved a problem he'd been struggling 

with for some time Archimedes was en3oymg the pleasures of his 

bath and was Just stepping out of the pool when the solution of the 

problem came to him hke a flash He was so overjoyed that he ran, 

naked, through the streets shouting "Eureka' I've found it, I've 

found it" Well, likewise, when young Champolhon one day had 

concluded he'd solved the mystery of the Egyptian hieroglyphics, 

he set out on a quick mile-run to the bmldmg where his lawyer brother 

worked, stumbled mto hIS brother's office, shouting "Eugene, I did 

it'", and flopped down to the floor m a trance where he 1s said to 

have remamed immobile and completely out for five days "Champolhon died on 4 March 1832, leavmg behmd the manuscript of an 

Egyptian Grammar and of a Hieroglyphic Dictwnary which, except 

for some errors of details mevitable m a gigantic work of decipherment and eastly correctable, form the basis of the entire science of 

Egyptology "-Drioton, "Decipherment of Egyptian H;eroglyphics'', 

La Science Moderne, August 1924, pp 423-432 

I shouldn't leave this brief story of the cryptanalytic phases of the 

solution of the Egyptian h1eroglyph1c wntmg without telling you 

that there rem.am plenty of other sorts of wr1tmgs which some of you 

may want to try your hand at dec1phenng when you've learned some 

of the prmc1ples and procedures of the sCience of cryptology A hst 

of thus-far undec1phered wntmgs was drawn up for me by Professor Alan C Ross, of London Umvers1ty, m 1945, and had 19 of 

them Smee 1945 only two have been deciphered, Mmoan Lmear 

A and Lmear B wr1tmg The Easter Island wntmg is said to have 

very recently been solved, but I'm not sure of that There are some, 

maybe Just a very few, who thmk the h1eroglyph1c wr1tmg of the 

ancient Maya Indians of Central Amenca may fall soon, but don't 

be too sangume about that either 

Should any of you be persuaded to tackle any of the still undeciphered wr1tmgs m the hst drawn up by Professor Ross, be sure you 

have an authentic case of an undec1phered language before you. 

Figure 16 .1s one that was wntten on a parchment known as the M1ch1gan Papyrus. It had ba:ffted certam savants who had a knowledge 

of Egyptology and attempted to read It on the theory that it was 

some sort of variation-a much later mod1:fication--<>f Egyptian 

h1eroglyph1c writing These old chaps gave it up as a bad JOb 

Not too many years ago, it came to the attention of a young man who 

knew very httle about Egyptian hieroglyphics He saw it only as a 

co .. ~Fl9E .. ~JIAL 64 

--
REF ID:A62856 

W F J<'HIEDMAN CONFIBEt~llAL 

Fig. 16. 

simple substitution cipher on some old language He tackled the 

Michigan Papyrus on that basis and solved it He found the language 

to be early Greek And what was the purport of the writing? Well, 

it was a wonderful old Greek beautician's secret formula for further 

beautifying lovely Greek young women-maybe the bathmg beauties 

of those days, among whom possibly were "Miss Greece of 500 B C " 

and "MISs Universe" of those days' 

The next period of nnportance m this brief account of the history 

of cryptology is the one which deals with the codes and ciphers used 

by the contestants m our Civil War, the period 1861-65 It is significant and important because, for the first time m hIStory, rapid 

and secure communications on a large scale became practicable m 

the conduct of orgamzed warfare and world-wide diplomacy They 

became practicable when cryptology and telegraphy were Jomed m 

happy, sometimes contentious, but long-lastmg wedlock 

There lS one person I should mention, however, before commg to 

the period of the Civil War m U S history I refer here to Edgar 

Allan Poe, who m 1842 or thereabouts, kmdled an interest m cryptog65 EOt~FIBEtnlAL 
REF ID:A62856 

CONFIBENTIAL HISTORY OF CRYPTOLOGY 

raphy m newspapers and JOumaJs of the period, both at home and 

abroad For his day he was certamly the best mformed person m 

this country on cryptologic matters outside of the regular employees 

of Government departments mterested m the subject 

In regard to Poe. one of our early columnists, there's an mcident 

I'd hke to tell you about m connection with a challenge he prmted m 

one of hIS columns, m which he offered to solve any cipher submitted 

by his readers He placed some bmitat1ons on hIS challenge, which 

amounted to this--that the challenge messages should involve but 

a single alphabet In a later article Poe tells about the numerous 

challenge messages sent hun and says "Out of perhaps 100 ciphers 

altogether received, there was only one which we did not unmediately 

succeed m resolvmg Tlus one we demonstrated to be an 1mpositionthat 1s to say, we fUlly proved 1t a jargon of random characters, 

having no meamng whatever" I wish that cipher had been preserved 

for posterity, because 1t would be interestmg to see what there was 

about 1t that warranted Poe to state that "we fully proved it a Jargon 

of random characters " Maybe I'm not warranted m saymg of this 

episode that Poe remmds me of a ditty sung by a character m a play 

put on by some undergraduates of one of the colleges of Cambndge 

Umversity, m England At a certain pomt m the play, thIS character 

steps to the front of the stage_ ang. smgs 

"I am the Master of the College, 

What I don't know am't knowledge " 

Thus, Poe What he couldn't solve, he assumed wasn't a real c1phera very easy 'out for any cryptologist up against somethmg tough 

If any of you are interested sufficiently to wish to learn somethmg 

about Poe's contributions to cryptology, I refer you to a very fine 

article by Professor W K Wunsatt, Jr , entitled "What Poe Knew 

About Cryptography", Pubhcations of the Modem Language Assocmtion of America, New York, Vol LVIII, No 3, September 1943, 

pp 754-79 In it you'll find references to what I have published on the 

same subJect 

Tlus completes the third lecture m this series In the next one we 

shall come to that mterestmg period m cryptologic hIStory m which 

codes and ciphers were used m this country in the War of the Rebellion, the War Between the States, the Civil War-you use your 

own pet designation for that terrible and costly struggle 

' 

COMFIBEHTIAL 66