• REF ID :A272 • 

This is to make a record of the date of conception of the following modification in the Navy Cipher Machine being studied in this office at the 

present time: 

1. Let there be added a Baudot tape transmitter employing the usu.al 

type of perforated tape. Let this tape be used for a running key, except that 

' only the follo~ing six permutations are employed on it: - - ~ - -, ~ 

_ + - - -, - - + - ,-, - - - + -, and - - +. The tape fil83' be of a finite or 

infinite length. 

2. Let the key-tape transmitter be used to control the action of five 

magnets each of which in turn controls the movement of one of the five cipher 

wheels. Thus, by use of the key tape, an absolutely irregular series of displacements of the set of cipher wheels would be brought into play, instead of 

a limited number of displacements, regular in character, as is the case in the 

present machine. 

3. Assume the five cipher wheels to be in a given initial position. 

Let the arrangements be such that with each depression of a key of the keyboard 

the tape step-forward magnet of the key-tape transmitter is actuated to move 

the key ts.pe forward one step. Suppose this next setting of the tape brings 

u.p a perforation in position -'.lumber 2; this would cause cipher wheel number 2 

to step forward one place. Thus, perforations 1, 2, 3, 4, 5 control, respectively, 

the displacements of cipher wheels 1, 2, ~. 4, 5. No perforation (blank) in the 

t~pe (permutation - - - - -) ceuses no wheel to be displaced. But this respective 

relationship is not essential; for by interposing a switchboard of the type covered in IDJI" u.s. patent number 1,522,775 of Jsnuary 13, 1925, the transmitter pins 

could control the cipher-wheel magnets in any relationship arbitrarily set up 

upon the switchboard. 

4. With a movement of the sort indicated in paragraph 3, the maximum 

length of tbe enciphering cycle for each possible initial setting of the five 

cipher wheels can, by proper selection of tape characters, be made equal to 26 

times the length of the key tape. If the tape is finite in length and consists 

5' 

of 1,000 characters, the cycle would then be 26,000 letters. Since there are 26 

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@'pp roved for Release by NSA on 11-01-2013 pursuantto E .0. 1352a 
• REF ID :A272 • 

possible initial settings of each of the five cipher wheels, the machine thus 

would afford 265 enciphering cycles each 26 ,000 characters in length. 

5. There is nothing in the foregoing which prevents the use of any of 

the variable factors now available, such as int er change of cipher wheels, wiring 

of the latter, wiring of left and right fixed sequencies, etc. 

6. There is no reason why the action of the tape should. be limited to 

displacements of a single wheel at a time; it is perfectly possible that one, 

two, three, or even all five V\iheels should be simultaneously displaced, depending 

u.pon the permutation of perforations on the tape presenting itself at a given 

moroont. 1.ihether such a system of multiple displacements would have an,y ad.vantages over that of single displacements is not apparent at this time. The possibility is merely mentioned for the sake of completeness of description. 

7. It is also possible that two key tapes of different length be used 

simultaneously, in two transmitters, interacting- to produce a latent resultant 

running key, as in the original A.T. & T. system. ~he disadvantages from a cryptographic point of view in this case are either entirely absent or, at most, are 

not nearly so serious in consequence as was the case in the original A.~. & T. 

system. 

s. Attached is a rough sketch to cover the simple use of one key-tape 

transmitter as discussed above, paragraphs 1 to 6 inclusive. 

Attached: 

Roue;h sketch. 

Witnesses: 

Disclosed to us on April 23, 1932, 

at \iiashington, D. C.: 

Willi&m F. Friedman, 

Cryptanalyst, 

Office of the Chief Signal Officer. 

~v~~ 1900 F Street, N. ·r., Washington, D. c. 

~~lf7~ !-r- 2

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New York Avenue, N. \'.., \'/ashington, D. C. 

~~uu Chapin Street, N. v.·., V.ashington, D. C,