EXECUTIVE DIVISION: 

MILITAR\~'\ITELLIGE:NCE.~RANCH 

In replying refer to 

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WAR DEPARTMENT 

OFFICE OF THE CHIEF OF STAFF 

Mro George Fabyan, 

Riverbank, 

Geneva, Illinois. 

My dear Mr. Fabyan: 

WASHINGTON. 

July ' 1919. 

As information has reached me from va s sourc s that you do 

not feel that M. I. 8 bas given t e result o our e forts on the 

A. T. & T. cipher the serious nsideratio t at ~ u believe it 

deserves, I have carefully gone over the en · e f e and offer the 

following as my views. In ord r that ther may b no further misunderstanding, I beg you to cor anything that ma~ seem to you incorrectly stated. 

text 

1918, transmitting 

her machine, I note 

d not presume to 

Secretary of War, expresses 

the messages sent in the A. T. & 

our statement the decipherby Mr. Gherardi of the .AmeriCompa:ny. is message, however, is No. 

ardi said wen, he sent it to you, 'l have 

that yo er nos. 2, 3 and perhaps 4. These, however, as you und rstand are not the arrang nt which we propose.' 

In lift:'. Gher rdi's letter to you of :March 27, 1919, he again 

stated, 'The me sages which you have deciphered are Nos. 2 and 3 

which I stated I had no doubt you could decipher ••••• vnien you have 

deciphered nos. l, 5, 6, or 7, something will have been accomplished 

in breaking the system in question.' 

I can find in our files no record of your having deciphered llfos •. 

1, _5, &, or 79 In view of this I nm.st agree with M. I. S's statement 

and the Secretary of War's reply to you that the foregoing offers no 

basis other than an opinion for Riverbank's contention that the A. 

T. & T. cipher is unsafe. 

As further confirrne,tion of your con•ention that the A. T. & T. 

cipher is not invulnerable, in your letter of 1'.ay 5, 1919, to The 

@'pp roved for Release by NSA on 11-19-2014 pursuantto E .0. 1352a 
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REF ID:A414~02 

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Adjutant General of the Army,--subject, 'Warning to the Department 

for the good of the service that the A. T. & T._Company machine is 

not invulnerable, and does not give the security claimed for it by 

the Department experts,' you state in paragraph 4 that 'Captain Powell 

is conversant with the A. T. & T. machine cipher system and we asked 

him to furnish us with four messages, using that system. Captain 

Powell did so, under the impression that they could not be deciphered. 

They were deciphered within two hours, and the clear text given to 

Captain Powell over the long distance 'phone.• 

However, in his letter of April 22, 1919, to Captain Manly, 

then in charge of M. I. e, Captain Powell states that before he enciphered the messages referred to you named the conditions and method 

of encipherment. I beg to quote from his letter: 

'Colonel Fa.byan asked me to encipher four test messages by means of two arbitrary keys of as many letters 

as I pleased, the second key to be one letter less than 

the first and the messages to be of sufficient length to 

contain three cycles of the two keys •••••• and ••••• 'I 

was also requested, contrary to what I believed to be the 

custom in actual practice, to return to the first letter 

of the upper key, When beginning the encipherment of the 

second and succeeding messages.' 

This gave you a variation of the real problem under discussion. 

The variation you were able to decipher within two hours; the real 

problem you have not been able to decipher after nearly one year's 

effort. Success in two hours and failure in one year spells the 

difference between incorrect and correct encipherment. 

If you will consider the foregoing I feel sure that you will see 

nothing personal; as stated in your letter of M:i.y 5, 1919, to the 

Adjutant General, in M. I. S's refusal to consider as important the 

decipherment by Riverbank of messages IlBde to order and admitted by 

Captain Powell to be enciphered in a m9.nner 'contrary to actual 

practice.' 

After all, if the enemy were attempting to decipher our messages, 

he would not be in a position to dictate to us just how they should 

be enciphered. As a matter of fact Mr. Gherardi gave you more information t~ I should be willing to admit would be in the hands of 

an enemy. He wrote approximately five hundred words explaining the 

method of the encipherment of each message, the operation of the 

machine, the humber of characters in the alphabet, the system of 

operation of the two running keys, and even enclosed a copy of the 

L_ alphabet itself, which can be clianged as can the key. To assume that 

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the ene:rey has all this information is to assume that he has an : 

agent in the code office, and an enemy agent in the code office will 

oause no end of embarrassment no matter how, or by what system, the 

cables are enciphered. 

You have now had 11r. Gherardi's test messages since,July, 1918, 

I appreciate the time and labor you have devoted to this cipher, but 

in justice to the Department experts I must state that it seems to me 

t:hat you have proved nothing not already known to them. 

The form of code or cipher the tepartment has used, is using, or 

Will use in the fU.ture, I consider a very dangerous topic for public 

discussion. Personally I do not approve of The American Telephone & 

Telegraph Company's detailed explanation of this oipher. The alphabets, 

the keys, the length of the keys, and the operation of the keys, 

should not and will not in the future, if my reoornmend.a.tions are approved, be known to anyone unless in the employ of and in the control 

of the War Department. If disclosed disciplinary action should be 

ta.ken. 

I can readily understand your letters regarding the responsibi~ity 

you feel in this matter. In order that you may no longer feel any 

fU.rther responsibility, I consider nwself justified in telling you, 

though as already stated I do not believe that information of this 

sort should be divulged to azcy-one not controlled by the War Department, 

that since shortly after the armistice of last November the use of 

the A. T. & T. cipher was discontinued. This I shall ask you to 

consider confidential. 

jcm 

M. CHURCHILL, 

Brigadier General, General Staff, 

Director of Military Intelligence.