Field Codes Used by the German Army During the World War
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IUSPllMH DAt'I 10 Feb 61 FILE OR From File of Special Consull:.allt (Friedman) SERIAL Field Codes used by the German Arm;/ during the World w· NUMBER Register No. 156 AND Sl/B.IECT Serial No. 1014 NAllB TO Mr. William Friedllan LI 10 Mrs. Christian• ~ ~ I'\. Geo. ' 1'lllft 'l'lUUCSFEBlUKO FILE TO Al'JOTHEI\ PBll.SON, COICPLETB " UftJllMIIZB PAPEJI AND PLACJI Df OUT-GODfG MAJL SERVICE Reclassified and approved for release by NSA on 05-19-2014 pursuant to E.O. 1352EI REF ID:A57075 Umol-huun tah-tiyal <William <:Judeiick yetel .eliuM Smith c:Fiitdman J; .. ·, ····-~-~ :-~i.;-~Bg).!-1-~1M . uy c11-b•11il ltubmbil tech s11me . ... _Thiumti@k. ~~~~.lOJ.. !.Jd!U~•KQ: ••. ~ · Ti ·#l/l1Wll,, 16jdilam-iz'a Io' ·100,, ··· k aot-beiag. you-tCNtn·give it ua, ~ u-""41 111.trJnl ah-11/#l • . ls-being~ our..ue by the expert. t~ I Classification changed to RBcJ'fH:I6'ff.Z) By ,Authority of HAROLD G. HAYES, Col., Signal Corps Acting Chief, Army Security Agency By '.A.SON G. CAl1PW&.L, lst Lt. 1 SigC l April 1946 ~w ;\CCOUN'rING m:C:ESSARY REGISTRATION CAfJCELED by Authority Hqs. A:JA ltr dated 2? Feb 46 2d. Ind ll Har 46, siened: liAHDLLJ G. UAYF...S, Col": 1 Signal Corps Acting Chier, Army Security Agency REF ID:A57075 30 April 1959 This document is re-graded '*Com':ffiEN'flkb" UP of DOD Directive 5200.l dated 8 July 1957, and by authority of the Director, National Security Agency. P~!#~ Paul S. Willard Colonel, AGC Adjutant General ' I0\4 \ REF ID:A57075 ' Register N'} 156 WAR DEPARTMENT OFFICE OF THE CHIEF SIGNAL OFFICE& WASHINGTON FIELD CODES USED BY THE GERMAN ARMY DURING THE WORLD WAR TECHNICAL PAPER By WILLIAM F. FRIEDMAN ~ Cld.t of Sflul laeell,__ Sedloa W11r PlaM and Tnilallla: Dl.WOn l1NITBD ST.A.TD GOVERNMENT PRINTING OPPICB wA.SBINGTON I lHI • REF ID:A57075 FOREWORD The information contained herein is printed from a report forming a part of the official files of the Radio Intelligence Division, General Staff, General Headquarters, American Expedition ary Forces. It was prepared by me when, as a member of the section mentioned, I was directed by Lt. Col Frank Moorman, then Chief of the Radio Intelligence Division, to submit a final report covering the technical work of the Code Solving Section of the Division. The present publication is practically an exact copy of the original report; no attempt has been ma.de to introduce technical information which has resulted from the labors of cryptanalysts since the days of the American Expeditionary Forces. WILLIAM F. FRIEDMAN, Cryptanalyst, Ohuj of Signal Intell-igence Section. OFFICE OF THE CHIEF SIGNAL OFFICER, WAR DEPARTMENT, Washington, June 1, 1934. (Ill) REF ID:A57075 ACKNOWLEDGMENTS This brochure on the methods of solving the codes and certain of the ciphers used by the Germans W6ttltl have been a1moat impossible were it not for the assistance rendered us by the code and cipher officers of our allies. In the exchange of results attained, we were by far the gainers. They have never hesitated to place at our disposal a.11 the methods and the results of their labors, without which, our efforts would have been very much less productive. It is a great pleasure to acknowledge our indebtedness to them'. Some of the material forming the basis of this survey is taken from reports by various officers who were members of this section, and due acknowledgments have been made to their work at the proper points. Specia.l mention is due to Capt. H. A. Berthold, C.A.C., for his invaluable assistance in instructing the officers who came after him in most of the details of the methods as regards codes described herein. In this work he may well be said to have been a pioneer. To Capt. P. B. Whitehead, F .A., are due my sincere thanks for his many suggestions offered during the course of my labors and for his kindness and invaluable assistance in proofreading the final copy. W1LLIA.H F. FBlllDIU.N, Fir81 LWutmant, M.I.D. GENERAL HEADQUA.BT!IBS, Au11mc.A.N ExPEDITIONA.BY F0Bc11s, February 5, 1919. (V) REF ID:A57075 TABLE OF CONTENTS Page A. Introduction ____________ .___ .______ .._. _______ ·_________ .: ________________ ·_ - ____ ---.-- _ _: __ - - - - _ - __ - _ 1 ~; General remarks on code __________ ·,: ______ .______ ·_·_· _______ ---- _ ----------------- _·_ ------------- 5 Q. Pre~ring the messages for ~tudy _____ -~--- _________________ -~ _______ .:_~-- -----------~---~---- _ 7 :ri. Recording and indexing the Three-Letter Code text--------------------------------------------- 14 I. Necessity for, and purpose of, recording_·-----------------~------------------~---------- 14 II. Methods of recording __ ----- _____________ --- _____ --------c------------------ --------- 14 1. Charts _____________________. ___ -------___ ._______ -----________ ---___ __ __ ____ __ 14 2. Record books _______________________ .: _______________________ .:________________ 16 III. Advantages and disadvantages of each system ___________________________ .:______________ 17 IV. The "Bible"-·- ____ --______________________________ ·_ _ __ __ __ __ __ __ _ _ __ __ __ _ _ __ _ ___ _ _ _ 18 V. Triptychs--------------------------------------------------------------------- .. ---- 18 VI. Extracts ___ ._____________________________________________________ ·______ ----- __ _ __ _ __ 19 E. Methods of solving the Three-Letter Code----------------------------------------------------- 21 I. Characteristics of the German field codes ________________________ -------- __ ------ __ ----- 21 II. The KRU codes. __ -------------- ___________ ------------------------ _______ --------_ 23 III. The uses and characteristics of the main classes of code groups ____ - _- ______ - ______ - _ - __ - _ 24 1. Numbers-------------------------------------------------------------------- 24 A. Uses------------------------------------------------------------------ 24 B. Characteristics_________________________________ --_____ --______ --------_ 25 C. Classification and identification _____________________ - _________ - - - _ _ ___ __ _ 25 2. Spelling groups _______________________________________________________________ 27 A. Uses------------------------------------------------------------------ 27 B. Characteristics_________________________________________________________ 28 C. Classification and identification__________________________________________ 28 3. VVordsandphrases ___________________________________________________________ 29 A. Military units ___ --------- ________________________ --------------------- 29 B. Interrogatives--------------------------------------------------------- 29 C. Prepositions_. ______________________________ - __ - - _ -- - - - - __ - • - - - - - _ -- - - - 30 D. Other frequently used words ___________________________ - _____ - _ -- ____ - _-_ 32 4. Punctuation·---------------------------------------------------------------- 33 5. Auxiliary signs--------------------------------------------------------------- 35 6. Blind groups----------------------------------------------------------------- 36 IV. Solution by analogy __ ------------ ____________________________ ----------------------- 37 V . .KRUSA codes---------------------------------------------------------------------- 42 1. Variants--------------------------------------------------------------------- 42 2. Additional number groups----------------------------------------------------- 44 3. Additions to vocabulary _____________________________________ - ________ - _ __ __ ___ 44 4. Table of hours of the daY------------------------------------------------------ 44 5. Nulls----------------------------------------------------------------------- 44 6. Additional spelling groups ________________________ ------------ ____ ------------- 45 7. Special enciphering table _______________________________ ---- __________ - _ -_-- _-_ 45 8. Cover-names (Decknaznen)---------------------------------------------------- 47 9. Distortion ____________________________________________ ----____ - ----- __ ------- 48 F. Length of time codes were in effect ___________________________________ ------ ----- ___ - _ -_ - ------ 50 G. Camouflage of liaison ________________________________ - _____ - __ - ___ - _ -- - - - - - - - - - _ -_ -- - - - - - - - - - 57 H. The nature and importance of practice messages------------------------------------------------ 60 I. Estimate of the Three-Letter Code------------------------------------------------------------ 65 (Vll) VIII Paa;e J. The Three-N"umber Code-------------------------------------------------------------------- 66 I. Foreword-------------------------------------------------------------------------- 66 II. Mechanics of the code--------------------------------------------------------------- 66 III. Initial "break" in solution __________________ --------- __ -------------------___________ 70 IV. Methods of solution_.---- ____ ---------- __ ------_----------------------- __ ------_____ 73 1. N"umbers·------------------------------------------------------------------- 75 2. Spelling groups--------------------------------------------------------------- 75 3. "\Vords---------------------------------------------------------------------- 78 V. Special method of solution----------------------------------------------------------- 79 VI. Secret keys and supplements--------------------------------------------------------- 80 VII. Actual operation of, and variations in, the system-----------.,---------------------------- 81 VIII. Estimate of the system-------------------------------------------------------------- 82 K. Extract from the Three-N"umber