• •• 

lit. D&vid X&hn. 

Windsor Gate. 

Great' Neck. Nev York. 

De&l' David: 

REF ID.:A70020 

e· 

•• 

f am sor17 that I .c&nnot accede to ~ ot J'01ll' r8Q118ata 

in 7omi letter ot June 13, as mch aa I vould like to. In 

connection with 7our question as to !hether 7ov soldier 

friend can get the Signal Corps bulletins and give th.em to 

7ou .. I do not think ha bad better t17 t.hat aa the lava are 

ve'1!7 a trio t. · . . 

We cannot a8Dd 7011 &DJ' •ter1al ot the kind tba~ 7ou 

asked about in connection vith boot~ggera during prohibition 

nor have ve &DJ' •terial tbat 7ou could vork upon duriJlg the 

aumm.er. It 1a thoughtful ot 7ou to volunteer t~ help. 

I can ~ppreoiate J'01l1' deaire to bave a photograph but I am· &f'lta14 we cannot •ke one aail&ble to 7ou. Ve 

are quite different from movie eta.rs 1D thia respect. but 

7ou can understand that this ia_neceas&l'J' to.r the aake or the 

vork. 

· Will.tam P. li'riedm&n• . Director ot .COJlllllUllicatiODB 

Research. 

@'pproved for Release by NSA on Ol-16-2014 pursuantto E.O. 1352a 
• •• REF ID~A70020 •. ~ 

HEADQUARTERS · 

ARMY SECURITY AGENCY 

Mr. Da Vid Kahn 

Windsor-_ Ga.te 

Great .I'leck, Nev York 

Dear Mr. :T.alm: 

WASHINGTON 25, D. C. 

18 ·January. · ).946 

. . I am sorry that I have been unable to.answer J'Our . - . 

. letter before this. I am ~lso sorry th&t I cannot· do 

. . 

bett~r for you in answering the questions y9u asked·t~ 

is indicated 1n t)le enclosure. It 1s not that I do not 

wish to give 7ou .~11 the 1nfo:rma.t'ion you desire, but that 

I cannot do so under regulation~ which are still applicable. 

l Incl.: 

List of ques~ions 

-

~er7. truly 70Ul".a, 

'WILLI.All P. FRIEDMAN 

Director ot .. Connun1cat1ons Res·earc~ 
,. 

9ookA 

ELEMENTA'iY' CRYPT-YSIS 

SOLYIN& 

SIMPLE SUBSTITUTION CIPHERS 

CIYPTo.IMDEX 

DAVID KAHN 

Windsor Gate PUBLICATION OFFICE and HEADQUARTERS + ROCHESTER, NEW YORK 

Great Neck 

New Yo A~t Editor, S-TUCJC 

Publisher, NEON 

Col. William ::F. Friellman 

O+":Pice ot'" the Chie-P Sj.gna.J Officer 

Heado.uartere, Army Service Forces washingt~n 25, n.c. . 

Dear CoJcnel 'Friedman: 

EDITOR, SHERLAC 

Cipher Editor, TRYIT 

Foreign Editor, EMPTY 

Perhpps you remember me. I am David Kahn, and wrote to you on 

June J3 as¥1ng ~or in~ormation, which in a letter (SPSIS-3) you siad 

that you could not give me. I fully ~~preciate why you could not give 

me the material, them, at least. • Uaybe, this time, you can help me •. 

Is there any information tha.t you can give me now concerning the 

Japanese codes, and the machine which deci~hered them? Is there any 

informaticn that you can give me concerning the ufe of' the Hageli_n machine 

during the war, by the Americans and Germane? I could go on like this 

forever, asking for: information on this particJuar thing or that, but I'll 

generali?e it, and ask: 

IS THERE ANY INFORMATION ABOUT CRYPTOGRAPHIC AlID CRYPTANALYIBIC :METHO~S 

USED BY THE UNITED STATES OR THE AXIS P01A'EF.S THAT YOU CAN GIVE ME, PRINTED 

OP OTHP.FWISE? 

... 

By printed information, I mean press releaees, etc., and by otherwise, 

ma.teTiaJ which you can give me in a Jetter. 

By the way, may I ask why cryptANALYTIC methods are so secretive? 

I •m sure the .Axis powers have a way of decrypting our messages_, so_ ~~a~ .. 

cifference would ~t make if tn~y r~und out the same thing,-~~or undoubtedly ·' . . .. 

they found the same ~eak points in the Hagelin machine that we did. 
2 

• • 

REF I~7~20 

Perhat>s in my ge ees to learn I'm over~k!ll things which I should~·' t, 

but if I am, won't you tell me what they are so I won't bother you again 

about them. 

CouJd you aleo send me ~s much material ab~ut the breaking of 

the Jap code and the Hagelin ma.chine as possible? 

Here are a number of pubJicatione which I read about in Dr. Galland 'a book, and. which, if you can, I wouJd Jike you to eend me. I have'. 

marked with a star ( *) those which he has marked as not bei.ng avai labJe 

f'or the pubJ ic, but his book was printed during the war, and it is. now 

peace. So I hope that you can eena r'e ·copies of them. Please note that 

the cne by Turkel is availab~e for distribution. By the way, can SignaJ Corps BuJJetins be bought now~ 

TUF.KEL, Enciphering with Apparatus and Machines, (trans. from German 

by War Dep' t, 6-?0-04·. 

' 

*~P.IEDMAN, EJernentary Military Cryptography, (1935 editiC'n~ Special Text 

*FT'IEDJl!.i.AN, Advanced MiJitary Cryptography (1935 EditiC'·n, Special Text 166) 

* 1"F I:SI'·MAN, Mi Ji t~:r.y Cryptana Jys is ( J 94 4) 

Wcn't you ~111 out the enclosed sheet and return it to me, aJong 

with a Jetter o~ your own whict. govee other in-f'o:rmation? Tharilo:; in advance. 

Very truJy ycurs, 

(./' . " 'i! J 

David Kahn 

A 

VERY :MERRY 

CHRISTMAS 

TO YOU