REF ID :A27289Ji 

\VAR DEPARTMENT 

OFFICE OF THE CHIEF SIGNAL OFFICER 

WASHINGTON 

February 27, 1934 

MEMO RAN WM TO 1 Mr. Rowe·, Fa.tent Section, Air Corps. 

(Paragraph numbers refer to correspondingly numbered 

paragraphs on examiner's report.) 

1. I see no reason for citing Dirkes et al. It has absolutely no bearing on present invention and deals only with an 

improvement in tape transmitters. I likewise see no reason for 

citing Friedman. 

2. Nowhere in Hebern is a cipher-key transmitter shown. In 

Hebern the movements or displacements of the code wheels are purely 

C mechanical; they are regular or periodic in character, and con0 trolled by ratchet mechanisms internal to the device itself. In . P present invention these movements are controlled by the cipher-key 

Y transmitter, in an aperiodic manner, by a tape which is external 

to and. not a part of the device itself. 

3. Make it read "an electromagnet and an associated ratchet 

and pawl, eaeh ratchet and pawl actuating the commutator with which 

it is associated, the set of commutator stepping mechanisms" ••• 

etc., e.s before. 

4. The examiner fails to distinguish between those parts or 

the mechanism which are internal to it {viz., the keyboard, commutators, cipher-key transmitter, indicating mechanism) an:l the external element which is the key tape itself. It is not claimed 

that the cipher-key transmitter is the external element; this part 

of the mechanism is controlled by a perforated tape; it is the latter 

element which is wholly external, can be removed, changed and varied 

at will. In all other cryptographs known to me the keying mechanism 

is internal to and a part of the cryptograph itself and therefore 

inherently presents weakness from the cryptographic standpoint that 

periodicity can not be prevented, since whatever the keying mechanism 

be (gears, cams, etc.) the parts thereof must operate upon mechanical 

principles embodying phase recurrences, or cycles, or periods. It 

might serve to clarify that which the examiner regards as "inaccuracy 

in language" if the following were added at the end of Claim 6& "and 

which consists of a perforated tape bearing ciphering characters in 

a plural-unit code." 

@'pp roved for Release by NSA on 09-13-2013 pursuantto E .0. 1352a 
REF ID:A272896 

5. Re Claims a, 9, 10 - Same comment as in Paragraph 4. 

6. I am not claiming Morehouse, but the combination or Morehouse 

with my invention. However, I would not insist on Claim 9 if examiner 

continues to object, but as regards Claim 10, the final clause "the n~ 

bars of such characters in the respective tapes being prime to one 

another .. constitutes an important improvement over Morehouse, from a 

cryptographic point of view. Studies have showed that if these numbers 

are not prime to one another, the full combinatory potentialities of 

the respective keys cannot be realized in practice. For example, if 

there are two tapes, one containing 1000 characters, the other 500, then 

after two revolutions of the longer tape the combination of the two 

tapes produces a resultant which coincides with the resultant of the 

first revolution. In other words, instead of having a single resultant 

key of 1000 x 500 = 500,000 characters the resultant is actually only 

2000 characters in length. In the case of keys whose lengths are prime 

to each other, the resultant has a latent length that is the product 

of their individual lengths. 

7. I thought such claims were allowable, but I am willing to drop 

them. 

a. Same comment as in Paragraph 4. 

9. We can add some descriptive data in the claims, but the aperiodicity is covered in the specifications. 

10 and 11. See comments above in Paragraph 4. 

12. Insert "practically" before the word .. non-repeating". Substitute "series" for "sequence". Add "said characters consisting or perforations permuted in accordance with a plural-unit code". 

13. In next to last line of Claim 23, c~ange the word "barstt to "keys~ 

I do not quite understand the examiner's objection that they 

fail to define the invention. 

14, 15, 16. These method claims are restricted to the mechanism 

covered by the present invention. They make no pretense of being basic 

and general, but are applied to a cryptograph having rotatable circuit 

changers of the type described. The examiner is certainly in error when 

he states (16) "Obviously no changes of character or condition are effected 

by the practi•e of the alleged method". In order to appreciate the real 

significance of the method of achieving aperiodicity in the operation 

of this cryptograph he will have to learn something of the science of 

deciphering without the key. 
REF ID:A2728~ 

• 

17, 18. You can best answer these yourself but I see many 

differences and distinctions between the claims cited. Claim 1 is 

differentiated from Claim 2 by the word Mmechanism"; the cipher-key 

trans1:1itter is one element, the mechanism controlling it is another 

and a separate element. Claim 12 delimits Claim 11 and is more 

specific, Does a claim to he valid have to cite a·different use for 

the same element mentioned in another claim? However, I am willing to 

drop 11, if 12 is allowed. 

William F. Friedman.