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MR. FRIEDMAN'S RECORDED LECTURE 

The talk today is to give you a bit of background -- historical background -- of a very old subject - cryptography and 

cryptanalysis. To give you an idea of how ancient this study 

is, I would like to tell you ~ little story which I came a.cross 

in an old book on cryptography. I don't know how true it is, 

but it is a good story and I would like to tell it. 

There was, it seems, an old queen in Persia about 2,000 . . 

'years before Christ. Her name was sJ,mArtm;s. She died and 

presumably went to heaven. She had had a great interest in 

cryptography, and at the end of her days she caused her remains to be entombed in a beautiful sarcophagus. On the outside of the tomb she had caused to be ~ngraved a cipher message~ 

and above the cipher message she had put the following legend: 

"O weary traveler, if thou art footsore, hungry or in need of 

money, unlock the riddle contained in the cipher message below 

and you will be lead to riches beyond all dreams of avarice". 

For many,many years the cipher message remained unread until one day along came a bewhiskered professor, I presume, 

who after much labor succeeded in unlocking the riddle. It 

gave him directions for entering the tomb and he got inside, 

and when he did so he found a box; inside the box was another 

box and inside the second box a third; and so on, until he came 

to a tiny box inside of which was a piece of parchment. And 

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this was what was written on the parchment, "O, vile monster, 

to disturb these weary bones. If thou hadst learnt something more useful than the art of deciphering - thou wouldst 

not be hungry, footsore or in need of money". 

And I presume that every so often each of you, when you 

come to examine your accounts probably think that the old gal 

had something. Now we will proceed with the slides: 

Slide 1 

Here is a slide which gives you a. rebus. Those of you 

as children, remember how rou would be interested in this form 

of secret writing: "Good reader as you older grow, you see 

, that is an old chair, you will learn what now you," etc. Now 

the alphabet and cryptography, I believe, came from this very 

early form of rebus writing. 

Slide 2 

In the Bible we find at least two instances of cipher 

writing: In Jeremiah, 25th Chapter, Verse 26, there occurs 

the expression:"""and the king of Sha.shak shall dr.fnk after 

them". And again in Jeremiah: "How is Sha.shak taken". Now 

for many, many years this name "Shashak" was unknown, and not 

so long ago it was discovered that if you take the 22 letters 

of the Hebrew alpha.bet and write the first 11 on one line and 

the second 11 on the line below you have set up a reciprocal 

alphabet for substitution; so that "Sha.shak", you will see, 

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translates BBL, Babel, Babylon. In those days, or course, 

Hebrew writing didn't have the vowels, those had to be supplied, 

and so we see that "Sha.shak" stands for Babylon. Below, I 

have a representation of another ancient form cf' cipher writing 

among the Jews - the form which is now lmown as "Masonic 

writing". The angles formed by the lines a.re used to represent 

the various letters of the alpha.bet. So, as you see 1 in the 

lower left hand corner, the angle opening toward the right 

stands f.or "A", or "l" and with the dot in it s ta.nds for "I" 

"' or 11 10" 1 and so on. As children, no doubt, you made use of a 

.2. similia.r type of design. 

Slide 3 

Among the ancient Greeks and Lacedemonia.ns, there was in 

use a device known as the scyta.le. The device is pictured on 

this slide, but is not correct. It really should terminate 

in a point instead of being strictly with parallel sides. The 

way 1n which they used the device was this: When the commander 

of the field forces left for his command he was given a scyta.le 

of certain dimensions and a.n identical scytale was retained at 

the war office. When they wanted to send a message to the 

commander they wrapped a piece of parchment spirally around 

the scytale, and wrote along the edges of the parchment, and 

not as is shown on this slide; so that in order to read the 

writing, theoretically, you would have to have an identically 

dimensioned scytale on which you would wrap the parchment 1 

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thus bringing together the bits of lines which go to make up 

the letters. It is interesting to note that the baton which 

the field marshal today carries around as one of the insignia 

of his high office, is derived from the scytale. 

Slide 4 

There are two forms --basic forms -- of cipher writing; 

one known as subs.ti tution, in which you replace the letters of 

the plain text with other letters or characters; and in the 

second form you transpose or re-arrange the letters. Here is 

a simple example of a substitution type of cryptography. This, 

I took from a Christmas card which was sent to me a number of 

years ago from one of the Signal Corps units. You will see the 

top line has three characters. It_ is in the "wigwag" code as 

it was called. T-H-E, and the next line reads, "season's"; 

"The Season's Greetings - etc". A very simple example of 

cipher writing. 

Slide 5 

In the next slide I have some examples of quite old forms 

of ciphex• writing. The top one is an alphabet which was used 

by Charlemagne. There are numerous examples underneath but I 

won't have time to go into these, because I think I have some 

better examples later on. 

Slide 6 

Sir Thomas More in his book about Utopia included at the 

end the type of writing which he called the "Utopian Alphabet" 

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and I thought it was interesting to show you what it looked 

like. I took this from a book which was published in 1524. 

Slide 7 

A number or years ago they came across a papyrus in Egypt 

which was very mysterious. The professors couldn't make out 

whether it was in Egyptian writing or some other form ot ancient 

writing, and for many years the significance or this parchment 

was unknown. Not long ago a young man without the wide background that the professors who had studied the parchment were 

fortunate to possess, came across this manuscript, and applying 

-the principles of simple substitution cipher finally succeeded 

1n deciphering the writing. It turned out to be the formula 

used by a gentl~man who apparently specialized in beauty work. 

That is, he was an ancient beautician, I suppose. 

Slide 8 

Now as old as that form or simple substitution :l.s, nevertheless, even today, we come across examples of it every now 

and then. You will remember only two or three years ago, there 

was a sergeant in the United States A:J.amy who was arrested for 

being connected with a spy ring, and this is the type or cipher 

that was used by this group -- simple substitution. You w111 

notice the characters are inter-lined with their equivalent 

plain text in Germ.an, and then the translation in English. 

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Slide 9 

~he idea of having multiple substitution came very early 

in the art. As you will see here, in 1401, there was used an 

aplhabet that :tiad multiple representation for the high frequency 

letters. You see four characters to represent "a" and four to 

represent "e" and so on. This is the earliest known example of 

that type or substitution. 

Slide 10 

It was indeed used by Mary, Queen of Scots, and this is 

an example or one of the alphabets used by her in certain correspondence. You will notice that there are two or three 

equivalents for some of the high frequency letters. 

Slide 11 

The "Porta Alphabetsl are well-known in the art of cryptography. They were invented and described by an Italian cryptographer named Porta, in 1563. This slide is a modern representation or those alphabets. You will see that there are reciprocal alphabets in the top section. The key letters "a" 

~ and nb" will represent that particular alphabet wherein 11 a 11 

is represented by "n" or "n" is represented by "a" and in the 

next section the key letters "c" and "d" will represent the 

keys where "a" is represented by "z" and "b" by "n" and so on. 

Slide 12 

I show in the next slide the form in which Porta set 

forth his alphabets in his own book. Those or you who care 

to see the original edition of Porta•s great work, and indeed 

he was a great cryptographer in those days, may see the book. 

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I have it with me. 

Slide 13 

This slide is turned the wrong way but it also represents 

a case in which the key letters can be used to produce multiple 

representation, or multiple-alphabet encipherment. That is a 

very old device used by Queen Elizabeth. 

s\IDE No. 2 

Slide 14 

In this case you will notice that the key words are 

optim~s dominus, and in order to represent a letter of the 

plain text you take the co-ordinates which indicate the position occupied in the diagram by the letter that you are 

enciphering. "A", for example, would be represented by "OD", 

and so on. 

Slide 15 

Many of you have heard about the Viginere Square. This 

was supposed to have been invented by a great French crypyographer a.nd described by him in a book about 1587. The square 

consists of 26 normal alphabets, simply arranged in cyclic 

order, with the plain text letters at the top and the key 

letters at the side. The book itself shows the square in a 

little different form. 

Slide 16 

Here you will notice that the key letters and the plain 

text letters at the top and side are displaced a bit and, in 
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fact, Viginere does not say that the key letters and the 

letters at the top have to be in norm.al order. He says you 

can mix those up if you wish to, and that is a point which 

has been overlooked by pretty nearly all commentators on 

Viginere's work. 

Slide 16 

Francis Bacon was very much interested in cryptography. 

In one of his earliest books, De Augmentes Scientarium, he 

published a description of a cipher system which he says he 

invepted when he was a youth in Paris, and that was over forty 

yea~s before. I found it interesting enough to show ~ou what 

it is about. Bacon says, draw up a biliteral alphabet - you 

w~ll see that at the upper part of the left hand corner of 

the slide - in which you have fiye "a's" representing the 

letter "an and •rr -.4 "a 's" and a "b" representing the 

letter "b" and so on. In other words, what you have here are 

permutations of two things through five places giving you a 

possible alphabet of 32 characters. But we only need 24 of 

' those. In those days "1 and j", and "u and v", were considered the same letters. So there are the 24 permutations 

which Bacon says we can use for a biliteral alphabet. Then he 

goes on and says if you want to represent a plain text word 

by means of such an alphabet, just replace the letters of the 

word by the permutations given in your alphabet. So you have 

in the lower part of the left hand slide an example, "fuge," 

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in which the letter "f'" is represented by "A.,A.,B.,A,B.," the 

"u" by "B,, A,A.,B.,B," and so on. 

Slide 17 

Now here is an example of' the way in whi.ch you would use 

such an alphabet in a very simple, rather amusing form. This 

was done for me by a doctor friend of' mine who got interested 

in the subject, and the bricks are of' two kinds, you will 

notice in this castle. Some of them are plain and some of them 

are shaded. And if you cinsider a brick which is plain as 

an 11 a 11 form and one which has shading, a "b" form, and start 

reading those bricks from left to right and from the top downward this is what the message says: 

"My business is to write prescriptions and then to see 

my doses taken; but now I find I spend my time endeavoring to out-Bacon Bacon." 

Slide 18 

Here is a further example of that same sort of' alphabet. 

Here is a picture. It might pass any sort of scrut:l.ny by a 

censor, but if you examine it ver-y carefully you will see that 

some of those officers are looking straight forward and some 

are looking to the left side or the right side. If you will 

assign the letter "a" to any of the officers who are looking 

straight forward,, and the letter "b" to those who are looking 

to one side or the other, and take them in groups of 5, beginning at the rear row,, the left hand part of the picture,, you 

will get the following message: Knowledge is power". That 

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incidentally is a picture or the first class 1n cryptography 

1n the United States operated 1n the last war. I had the good 

fortune to be director or that school. It was out in Chicago. 

Slide 19 

Now, Bacon goes on to say that that is a very simple 

scheme, but we are going to make it a little bit better. We 

are going to show you how to enfold a message 1n an external 

text so that it will not be evident that you are conveying a 

cipher message, or a secret message. So he draws up what he 

ca1ls a bi-formed alphabet in which you have two kinds or 

capital "A's" and two kinds or small "a•s" and 2 kinds or 

capital "B's" and two kinds or small "b's", etc. Then if you 

will take those capital letters or the two different kinds 

and the small letters or the two different kinds, and manipulate them in accordance with the requirements or the secret 

message which you want to enfold, you can put across, externally, an innocent-looking message, but it will contain 

an internal secret message. As for exam.P-le, in this case: 

PVl-o ..:.tCl-C.. ~ 

Here is_ a message which reads "Berta terrais" etc. "All is 

lost; :Mii'oris is killed; the soldiers want food; we can 

neithez- get hence noz- stay longer here." It's a difficult 

situation to be in. But here is how he enfolds the message. 

On the right hana side, you will see the external message in 

which th.at secret message has been enfolded by a proper use 

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or the two different kinds or type. 

Slide 20 

Now I have often had people say to me,, "Well,, that sort 

of thing is pretty far-fetched. I don't think that anybody 

could get away with a secret message enfolded in that manner 

t\ 

today~ But I think that it is possible. For example,, here is 

a paragraph which I put in one of the texts which I wrote a 

number or years ago,, and it contains a secret message,, and I 

doubt very much whether anybody would suspect that it does 

contain a secret message. In fact,, if I hadn't put the footnote 2,, there which reads" "the sub-paragraph which the student 

has just read contains a hidden cryptographic message. "With 

the hints given in paragraph 35e,, let the student see if he 

can find it~ In fact I believe if I had not done this,, nobody 

would ever suspect that it contains a secret message; and 

even with that hint there have been very few people who have 

solved and found the secret message. I won't give that message 

to you right now. 

Slide 21 

Thomas Jefferson used a simple code. In fact it is what 

we call a syllabary, today. Here is a section of that syllabary. You will see that the plain text words are represented 

by combinations of digits. This is the deciphering section of 

that syllabary. You will see that the numbers run in numerical 

order and are accompanied by their meanings, and those are in 

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ra.ndom order. There was, of course a.n encoding version in which 

the words and the phrase~a few or them, a~ranged in alphabetical 

order accompanied by their eqtivalent code groups in random 

order. 

Slide 22 . Here is a pictUl'e taken from a rront?spiece or an old 

book or cryptography, dated 1794. The lady at the desk, I 

presume, 1s the version or the WACsthat they had in those days. 

The gentleman who is dictating to her is giving her a plain 

language message to encipher. She has before her something 

which is labeled, "Table a Cheaf"riet!J'"! I guess she is enciphering the message, and in the cabinets and drawers alongside the wall you see the various keys or key lists that were 

used in those days. At the top you have bottles or containers 

that no doubt contain secret ink materials. 

Slide 23 

This slide shows a photograph of a message which is known 

today as the Benedict Arnold "indecipherable cow" letter. Nobody has suceeded in finding the meaning of this message. 

Obviously, there isn't enough of it here to do anything with. 

The secret meanings of certain of the words were agreed upon 

between Arnold and his correspondent. The message begins, "I 

have bought a cow and calf from General John Joseph Bullus~ 

and so forth. I don!t think that anybody will succeed in deciphering this message. I show it merely as a matter of interest. 
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Slide 24 

The use or cryptography had considerable stimulus during 

our Civil War. Here is a.n instrument which was used by the 

Confederate Army, captured at the Battle of Vicksburg. Cryptographically it is nothing but the Viginere cipher in which the 

Viginere table has been wrapped around the ·cylinder and the 

pointers that you see on the bar at the top can be slid into 

position, one to represent your plain text letters, and the 

other to represent the key letter; and then you could rotate 

the cylinder forward or backward as you had to find the letters 

involved. 

SJ.ide 25 

This message was supposed to have sent by President 

Lincoln in 1862. It is addressed as you see to General Burnside, Falmouth, Va. And if you read it from left to right, 

it doesn't make very much sense, but if you will read backwards you will see that it does contain a pretty good message. 

"If ;r should be in a boat of'f Aquia Creek at dark tomorrow, 

• Wednesday evening, could you without inconvetn.lence meet -see thec.u~~D 

tl~sh represents.meat - and pass an hour or two wi.th me. A. 

Lincon.n." I don't know how authentic this is. I came across 

it in a secret British text on cryptography. 

Slide 26 

The Federal Army used a cipher known as 

In this form they would have a design or certain dimensions --

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certain number of columns and rows and the message would be 

inscribed in that design and taken out by following a certai.n 

route as you will notice in this case of this example. The 

top diagram begins with the number one in the lower right 

hand corner. After you had written your message in that 

design you woul? take the words out by taking the last work 

in the last row and then going up the column and then diagonally to the left and so on. In addition, to that simple 

form or transposition they had arbitary groups which represented the names of important people. For example, the president of - d the United States was represented by Adam or Asia; 

~ ~ the secretary of state by Abel or Austrla, etc. 

Slide 27 

Here is an actual message which was sent in a system of 

that sort and addressed to General Grant. "For U. S. Grant, 

no expedition to Texas will be undertaken," and so forth. 

SIDE 3 

Slide 28 

The period of the World War we come to next, the first 

world war. I want to show you some examples or the cryptography used by the various belliger6nts. 

Here is the type of cipher used by the Russians. The 

plain text alphabet is seen at the top and then underneath 

are several rows of cipher equivalents composed of two-digit 

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combinations. The key is shown in the first column - 31456782, 

apparently taken from about 10 different lines of numbers 

and rearranged according to the key for the day. The table 

below is the deciphering version or that same system. You wtll 

notice that in the enciphering version the equivalents for 

the letters are in random order so that you had to have a deciphering version of the same system. You will notice that in 

the enciphering version the equivalents for the letters are 

in random order so that you had to have a deciphering table. 

Slide 29 

Here is the type or cipher which was used by the French 

Army at one time in World War I period. They had a transposition rectangle made up or a certain number of columns 

with the day numbers at the top and instead of taking the 

letters out or the columns in simple key number order, they 

drew diagonals through certain places in that diagram and 

took the letters out of the diagonals first; and then they 

took the remaining letters out of the columns in key number 

I won't undertake to go through this example, but you will 

see that it is a bit more complicated than simply taking the 

letters out or th~ oolumns in key number order. 

Slide 30 

The Italians used a modified form of Vigfn~re square. 

Here it is. Instead of having letters to represent the 

letters of the plain text they had numbers, but the basic 

principle of the scheme is exactly the same as the Viaginere 

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square which I showed you a few minutes ago. The numbers internally in that square, you see, run in strict serial order. 

Slide 31 

The Germans used a form of Cipher which we ca.11 the "adf gvx" 

cipher because the text of the messages consisted solely of .the 

letters "a.dfgvx". The method of encipherment is a.s follows: 

Suppose you had a message, plain text: "request reenf'orcements 

immediately." There would be a. square with the key internally 

disposed in the lines and columns as you will see at the upper 

right ha.nd corner. In tha.t particular square the letters rea.d 

to QU, I can't ma.ke out the next one, 5ST, etc. dlsa.rra.nged 

internally. The co-ordinates a.re in normal fashion, a.dfgvx, 

both a.t the side and at the top. Now you encipher your 

message first by replacing the letters of your plain text by 

the two letter combinations given by this cipher square. As 

you will see the line marked biliteral substitution, ".!:" is 

represented by 11 xd11

1 

11!:!_11

1 by 11 a.f 11 , "q" by "a.a" and,, so on. 

The next step is to ha.ve a key word from which you der:1.ve a 

sequence of numbers in disarranged order. You will find ,, alongside the expression "key word": the quick bro-wn fox 

jumped." And the key numbers 14, 16, 61 2, etc. derived by 

numbering the letters of that key sequence in accordance 

with the position the letters occupy in the normal alphabet. 

Next thing is to take the two letter equivalents for th1.s 

plain text message and write them underneath the columns and 
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the diagram formed by putting down those key numbers. As 

you will see the letter "r" i.n the upper pa.rt of the diagram 

1.s represented by "xd", so you have "xd" in the first two 

positions of the .first line of the final di.a.gram. Next comes 

"af", "a.a", "ad", etc. When you have finished writing out 

those two letter equivalents in that fashion then you take 

the letters out of the columns 1n key number order. In this 

case, the message begins "adaf". You see where the column 

is headed by the digit 1, so that you will see what the transposed text is like. That is a pretty complicated cipher and 

I might say that in those days this cipher was used by the 

~igh command for only its most important messages. We didn't 

know in those days how to solve this type of traffic unless 

there were some special cases to work with; for example, 

messages which began alike or messages which ended in a 

similar fashion. But nevertheless, andrespite the fact that 

we could only handle the traffic when we had those favorable 

cases, we did succeed in reading approximately 75~ of all 

the traffic that was transmitted in that system. 

Slide 32 

Now we come to a bit about code. Roughly code is a 

type of cryptography in which entire words and phrases, sometimes entire sentences, are replaced by groups of letters. 

Here you see an example of a type of code which you can 

obtain by going to a telegraph or cable office. This is one 
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• put out a number of years ago by the Commerfc~l Cable Company. 

The code groups you see in the heavy black letters are all 

five-letter groups. They differ from one another by at least 

two letters. If you will take any one of them you will find . that there are two letters which distinguish that group from 

any other group in that code. The method of use of course if 

very simple. You replace thew:>rds and phrases that you wish 

to transmit by the equivalent code groups as you find them in 

the book. 

Slide 33 

Now there are all sorts of codes suited to different 

businesses, speciali.zing in rubber, textiles, automobi.les, 

etc. Here I show you a slide of a code used in China called 

the "Official Chinese Telegraph°'Code 11 • In this example the 

characters are disposed in regular rows and columns 100 of 

them to a page and each character is represented by a number. 

A very simple method of use. 

Slide 34 

Here is an interesting example of a highly specialized 

code. There are as you know lots of people who beli.eve in 

the treatment of d:l.sease, not by means of medicines, by by 

the use of proper words; and here is a code gotten out by 

a meta physician who believed in the treatment of disease . by the word method; and he fixed it up so that even if he 

.. 

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was away, or if the patient was away, he could treat the 

patient by means of the proper message. In this he was 

apparently well versed in some of the phases of practical 

cryptography. His code groups show not only a two-letter 

difference but a three-letter difference. He realized that 

it might be pretty serious matter to have a mistake made in 

transmission. and so he wanted to insure that the mistakes 

would be corrected. It would be a rather serious thing if 

you were to think that you were suffering from delerium 

tremens and got treated for coma. 

Slide #35 

A French Army Code of the World War 1 period. Here you 

see the plain text codes are in alphabetic order accompani.ed 

by code groups in random order. The groups in this case 

being 4-digit groups and therefore thissort of a code required two parts, an encoding version and a decoding version. 

This is a picture of the encoding version. 

Slide #36 

The code used by the German Army. I think I should 

mention that in the World War 1 period the use of code books 

did not begin until about 1917. It was thought at that 

time that the code books could not be produced in the field 

and nobody tried it until the Germans first came out with one 

the latter part of 1916. This is a picture of a couple of 

pages from the codebook captured in early 1918. The plain 

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text words you will notice are in the left hand side of the 

columns and the code groups at the right. In thi.s code, the 

groups begin with the letters "K-R-U-S-A", so we call it the 

"Krusa" code. You will' see that some of the words have more 

than one equivalent, and at the bottom of the page you see 

wh&t are called 11Blinde Signa.len", which means "dummy groups~' 

Slide #37 

When the .Amer:tca.n Army first got to France, they were in 

a rather bad way for codes. Here is an authentic example or 

a code made up under the circumstances and it is rather interes~ing to me. You will see that was used by the 52nd Infantry Brigade dated 17th of April 1918. If you wanted to 

indicate "casualties", the word "killed" was reported by 

"strike out"; "seriously wounded" - "base on balls", "slightly 

wounded" - "hit by pitc~a.11". In the lower pa.rt I notice 

some very interesting names probably of no significance to 

most of my audience. I wander if anyone of you remembers 

who Johnson, was or Leona.rd or Wagner, etc. 

Slide #38 

Here is a picture of a page from a British field code. 

They had the code sectionalized. Here for example, is a 

section on "gas and gas attack" relating to our forces and 

long phrases in complete sentences representedby 3-digit 

groups in numerical order. This, of course, requ:i.red enciphe1"lD.ent so that it was a two-~pprocess for them. 

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, 

Slide #39 

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TOf' SEORE'P 

Now when the Americans came, we didn't havem.y codes, 

as I told you, but we first began using what was called the 

11 playfair cipher 11 , copied from tl:le British, as a matter of 

fact. Here is an example of how the "playfair cipher 11 operates. 

You have a keyword which is inscribed in a square with the 

rest of the unused letters of the alphabet in a normal sequence. This square happens to have only 25 positions, so 

that the letter I and the letter J are treated as the same 

letter. Now, if you have a message "The enemy moves at 

dawn" and you want to encipher that, you have to follow 

certain rules for drawing up your equivalents. The letters 

"TH", for example, are represented by "HW"; a diagraph:l.c 

cipher in other words. I will not undertake to tell you 1.n 

detail how this cipher operates. 

Slide#40 

Well, as I told you, we first started out with the 

11 playfa1r cipher" and then we began making up codes and 

here is an example or one or the field codes printed at GHQ .. in the AEF. These codes were replaced every ten days and it 

was a great source of astonishment to our British and French 

allies that we could do that. They were unable to produce 

their codes nearly as rapidly as the Americans could. Here 

you see the words are listed 1.n alphabetical order, accompan:I ed 

by their code groups in random order; and there are many 

variants. 

SIDE 4 

'f OP BBOHE~ 
Slide #41 

REF ID:A70308 

'f OP SEORE'f 

Now we are going to take a few examples of types of 

ciphers which were encountered i.n the last war by censorship. For example, here is a card whjch was mailed in New 

York on August 8, 1916 addressed to a Mr. Charles Mcalvin, 

in London. 

Slide #1~2 

Now on the back of that card there appeared some wri.ting 

in German, but if you read it as it runs, why, it doesn't 

make any sense. 

Slide #43 

However, if you apply to the text a grill, which is 

a device containj.ng apertures in certain positions, then 

(Slide #44) 

you see that the words of the messages come out in the1.r 

intended order. In this case, it reads "Lieber Charles Zei 

Mit, etc." "Dear Charles; Be very care.ful with the .following 

secret message." 

Slide #1!:,2 

And you could apply that grill in one or all four 

posftions that are possible. Now here is a form o.f cipher 

writing using music. Many people think that we have something brand new and suggest that it would be possible to 

convey a secret message by means of an apparently innocent 

sheet or music. This actually comes from a very old book 

of cryptography. Nevertheless, every once in a while we do 

'l'OP SEORE~ 
REF ID:A70308 

'!'OP ffi!!Offi!l'f' 

run across instances of the use of musi.c for conveying secret 

messages by people who are unskilled in the arr-;of cryptography. 

Slide #J'r6 

Here is a map wh:i.ch was found on the person of a spy in 

the last war. It is a map of a city in Denmark and nothi.ng 

particularly not1.ceable about it except that if you examine 

it very carefully, you will see dots and dashes along one of 

the tramways. Now when those dots and dashes were written 

down, 

Slide #fl.. 

they still didn't make sense, but as you will see, the elements 

of a simple substitution cipher have been applied to this thi.ng. 

The top line of dots and dashes are in the Morse equivalent for 

the letters BTADC and so on. Then if you apply the part:1.cular 

type of cipher alphabet involved in that, the BTA comes out 

"OEL" the word "oil", "Oil has been received and everything 

is ready." 

Slide #48 

Many people have an idea that they can enfold a secret 

message in an apparently innocent text by putting the secret 

words in certain positions, every 4th on every 5th etc. and 

here is an example of a case where a person intended to have 

every 4th word make the sense of the secret message; but the 

clue is given in the second and third 11.nes of the first 

paragraph. You see how the word fourth stands out in the 

'l'OF 8ECHE9? 
REF ID:A70308 

'i'OP 6EiOREi9? 

mi.ddle of the second line and the word 11word 11 at the beginning of the third line,, so that the clue is the "4th word 11 • 

Now if you will take the {Slide #42) message in the next 

paragraph and read every 4th word,, you will see that it reads 

"Great gain in arms al though s ti.11 very far etc • ) 

9?0P 8:SORB9?