., 

I I 

; 

! 

to touch upon all pbaaas. o~ code WOl'k. Bence I shall oonline myself chiefly to 

those phases Which will p.robablY" at aome future ts.ine aoncer.n moat o~ those present; 

namely, the aategaarda and preoaut1Qns 111'i1ch must be observed in code or oip~er .. ·. 

operations in order to maSntaln the secrecy ot the system ot carmmmioation a.d01>ted. 

A. preliminary. word ot expl.a.Dat ion with regard to the two terms "Code" 

and "Cipher" may be naceBaal"1• ~- moat . of you. the no words mean practically the 

same thing, but aueh is not tbe case. Modern cryptography draws a ratbe.r sharp 

distinction between the two terms. 

A CIPHER, taken in a broad aenae, la the name applied to any system of 

017'Ptograpby which· involves the transformation of the individual letters of the 

orle;inal, intelligible text ot a meaaage into a secret or uintallillble form by 

means of previously eate.bliahed agreanenta Whloh subsequentl1 perm.1 t of the recon-

· 1. 

atnction of the original ta~t from the sec-rat tm:t. 

~e orlgiDal, intelligible text of the· message is called the PLA:m TEXT~ 

'lhe re11Ultant un-1nt&llig,._b~e-...or seer.et. text. is oallad-.tbe CI;P.RER TEXT. 

The operatlon ot transtornilng the Plain Text into the equivalent Cipher 

Text 1s called EnclpherlziiU .. the reverse operilion. fa oal~ed-· Deciphering. 

A CODE la the name apPlled to a speclaliBed a19tan of cryptography Which 

involves the tr~sfo.nna.tlon o~ .ih-e original, intelligible plain text of .a message , 

lnto a secret or unintelligible form by means of a book or a doaament which gives 

conventional words, or uniform, arbitrary· combinations or numbers as the equivalents 

ot not.only the lette~s, but also the words; phrases, or entire sentences .of the . r 

original text. It la obvious· that identical copies ot the Code or Code book must 

be in the possession ot the correspondents.. The operations Which apply to this 

system are.c~led ERCODDIG and DECODIJG. 

. While there a.re some ciphers which resemble code or tend to approach 

, 

coder yet the distinction which exists and Which should be made between cipher and 

code is thia; Sn cipher one deals with the individual letters as units; in code, 

While one may deal occasionally with the lnd1V1dual letters, the ,operation is 

·' 

lA\pproved f,or Rel.ease by NSA on 11-18-2013 pursuant to E.O. 1352§ .. \ I • 

. 

\ • 

I 

I 

' 
REF ID:A66639 

pr1no~pall7 COJ'1C81'Jled with tbe phrases or sentences taken aa unlta. 

. . When the code designations ot the encoded worde ot a message are afterwards . ' ' ~ 

'enciphered t of in other .'tVOrds' 'When a message 1 tt' first e:nooded and th~ the code ' 0 o ' I 

equivalents are e:rioiphered, ti;ie re.W.t· la called EW-0~ ~ODE• Poi example, 

i:t the.code word for ~he phrase, 11.Bt ~rder ~t the C0mnanda~in•Chief" la POBAL, . . . . . ' ' 

end 11' .5hia· code. word is then enciphered 1nto the form CI'l'AX or lnto the number 

17521, the latter ls ·th~ knOm as ·f$91pbered co~•· · 

- ·-- .,.. ·_. ...... -· so tar· as 'l am·awa~, a •7-stem .. ot secret: oonmunication Which .ts_~bsolu~~ly ____ _ o' o ', o ' o I 

ilnPr~gnable.againat solut!on bi' the enemy and 'Whloh at·tba same time is suited to ' , 

the needs ot naval, mlllta.ey, or diplomatic ottl_oea, is not known to the ao1ence 

o~ cryptography~ I do not know how SU:ftlciently to bilpress upon 10Ul" mlnda the .. neeeaa1ty tor exercising the moat rlgS.d and pa1nstak1ng care S.n the use ot the codes ' . . ' 

or o1phara Whloh inay at some t1lture t1m& be entn1ted to you. I have ae>en elaborate - ' . 

code and cipher 91stems rendere~ absolutel7.valualase through the carelaasnesa and ~ ·: . 

lgnoranoe ot one man. l'l'om the point ot view of the Intelligence Depa.r1iment it 

seems to me t~t a man Who flagrantly_ disregard& or violates the rules and regulations 

laid.down by. th~ __ Q9d! __ .an4 S~pal .. Sectic;tn .. is as de.aerv1~~9( ~a eX:treme ,PW11sim{ant _!or 

a breach 0£ dici~line·resa.lting ~n the actual or potential loss of life.of his comrades 

as ls the man Who conaci~usl7 betrays tham l>y . .furn1ah1Dg 1ntorma.t1on ta .the enemy. 

Le~ me tell you· ot one instance Whiob to my knowl:edge had disasti"Oua consequences. 

' . You wlll recall that in March· 1918 the Germans launched their last and greate1't oftene1ve on the western front• Caref'ul. preparations and· provision liad been made 

tor nearly e-yerythlllg. On the da.y ot the opening ot the ottenalve an absolutely new 

type· of code went into ettec·t in eveey sector simultaneously on the Whole front .. ;" ' . ' 

Months ot wark b7 the illied intelligence depa.rtmentSupon the German treneh code were 

· · rendered worthless at one stroke. We had to begin all over age.in and Whll:e the 

general e1tu.at1on \in the 'Vllhole battle tront looked very dark• dvlng those cr1 tics.1 

weeks• things looked espec1all1 dark to.the member& ot the cod.e and pS.phe~ ~action. . . 

Among th-e veey ti.rat messagea.,-ln the new code that were ·intet-b.epted. by I ' ' ~ 

· our own Signal Oo~s we.a a. set ot three messages pasa~ng betweep; two .ata~lqllB opp<>slte 

the fron~ held by the ~erloa:n forces. He~ they are $ .... u ............. ~.,..~·-u***•** u 

Thie solution was ot vastly greater 1mportan().e than is a:ppe.~t on .the . ·. . \ 

face of the decoded message. The message itself meant,. tor us, at least rloith1~ .• 

\ '. 

' \ 

Even to this dq I oan onq 8Ul'm1se Wh.a t it meant. But the most important featl;tre' 

J' ~i~~ . . • . . . I \ ', "• 

! . ·r ...~ · ,n \. .. ,1 '\ 

.. 
REF ID:A66639 

.3.· 

of the message was· that lt at once gave definite clues ·with _regr~ .t~. ·the. nature and . . ( 

meohanic.s of the· new ay&tern41 . Oer.ta.in features ot the groups ·1n·'.tbla 'mea~age ~~.l to ~. • • • • I I . 

the mald.Dg .of some ~ssumptio~ Which we~e· teste·a. upon other. meas~es;. tliey proved to ' \ o ' f I • ! ' 

. . \ .. : . . ·. ·. . : ' .. 

be correct.. At one blow the Whole ne\V qatem fell like a house ot cards~ · .. ' I • ' ' ' ' ' ' ' ,' ~ I • 

. .. . .. . ~ 

· · I have ~id that this 'message meant notbi:iig to us; it·ma.y ~ve:meant but·· • : • • • ,• • J 

vsry little ~re to tiia·Germana. be.~ whom' ~he mea~age WB:S. exoha~ed. :Bl:lt ·this . : ' 

'I:° I 0 ' ' •, I I 

meaaage led to the bre'alitng ot·th,·Whole' oode. Certainly the Gez:m&n·operator wo~d 0 ' , I , .,. 1 , , , I , I , 1 r , ~ • 0 

• I ,• • I J 

· not ·have colDl'l!.itted 

I , 

.1!hla l~~ab~• ' ,._.. - ' ' ' ' I blunder 

' ' r 

·had th' i;ne11age 1'•en ot ·g~ea~ ts.~tloal 0 ° ' 0

1 ~ ' , ' ' • • -.•~ - .._,, I' 0 .._ '' "f" - • - .. 

o I • ' I I , o o ' 

• o I • I o ' I o ' 'J • ' 

. lmport~e ... But ~or the ~ode aol~er. all·~asages are ot e~ual. impo~t~~+ -·and moat · ··. ' . . .... 

oft~ the massage~ ,r,;f .least. ~?naequence as regards· the tactical· al tu.a.ti~+.• y1el~ 'the 

' .• '·> 

moat :tar r.eaoh1ng.·re~ta .· and are. there.tore ,the mo~t diaa.i:t;roua a.a·: far aa ma.lntalnlng . , . ·. . .. · ' f' ,..., • 

' , . ~ lo'\'. Q\·..B>.. 

~ol"';'C!-~ U, ~...,~._I~ • ... A • ~ ~,J t_ ·l:i_~ 

the ....... .,,. of the Oode l.o OOllC~~ •. (~r,a9tl,~·-~~S~<l~·f ~~· ~c~~ 

~~i.M..,.'1 \I"~~ I might add: ·t~~ ·~o ~~Pl.e~.e the ·dramat1~·-~1tuat~on rasW.tant u~n the ~~ 

solution of this firs·t' ~saage, the naw.i., toie~her w'itb the datt, was s~t to ~he~':!"""~ 

.general . hea4:q'1arters !'-"" ot .. ~ '• al.li~a ~ . s~clal ae~o-plan~ . b~auae ' at that 

'· 

t~ dire~~.~ ~I>,,, 

. . WJ,,,; talegrapliio communication between the American and the other code otticei had not yet.P~ ,. . . ~::{4 ......... been eatabl.1ah8d. · ·. · · ~ . . • ,,.._, , ... -' I .·· . c.v---Y:..e ~~N 1:. "·It - ,. ~ '- ,• _.!: -:, .F-7 •.' •" •,' •• ;~ ~( •r ~ 

'How·~ o~·'hts co~ades lost the:1r live& ·a~ ~ ~li'e'~t- reeul t .of'. thls one 

.N.! .... rJ ; ,.~f-'-

German• a- blunder, no o~ can ·sa1~ · He wa~ guilty o~ viola t.ing o~. ot .tb,e :mos~ ' I ' ~ 

important rules · ot ·code work• nameli, a message oriq~t t~ans~1 tte~ in ~~de'. or o lJ?her 

. ' 

must NEVER be repeated ln ap;r other form ~·taoever. 

If it ·~st be repe~tad be.cause, o:l p~ilation. or ·garbles., an :~~ct dupl.1cate • ' ' • I • .. I ' ' ' t;. : : ' • j I • 

.ot the original' code or cipher text must be s·ent. lt ~fter aevara·1 rept.tltions the o ' ' o ./' ' • • ' ', ' I ',• .: ( 

~·s~e is still unintelligible, beaaus~ ot a .failure on tlie J>ar·i.' of the}reaeivl;ng . . I 

station to _be ln poiseasion of the necessary !iata tor decod~ent,, then 1t_ma.y be" . . ' 

necessary.to transmit th~ message ln·an~ther torm. ·Wh.a~evei" this-second: form be~ it. 0 ' I I I ' ' ' o • f ~ •, • < 

should bear no ~eaemblance wha.tso~ver to the tirat mess&g• as regards in~ernal form 

ot the pla1n text Which bas been ~nooded ·or enciphered. In other words ,j the'·plaln . I·. 

text ot the or1~1Dal .mes.sage ~at be altered 1n torm to· the greatest extent po~sibl~,. 

' ' . ' . . . ~ 

. o~naistent ~~th the. intent an~ me~ing .or the .maaaag&. Th~s proeea1,t ·ot 8.l taring_ the ,• 

. . plain c.onte.il~•· of' .a mesaage tor 'the purpose. of ~hangi13g its t~rm,. wit);lou'J; .~ter·ial • ' .. I • ' ol •I 

0 .... .-.•I ' I I I I • • 

cha.Zlge· bi meaning,. a~ that. a close compa.ria~ .be~een the p~ln .t.ext ~: ·1ts ' 

. ; . . . . : ,, . ) . \ 

'\r~1 

equtva:~ent cod~. or'. c·ll>her tax~ ~ill be 1mpoaaib~f>~1s called .P~S~G~. ;l shall \\. 

refer to it later. As tar .as .possible no infoimatlon should.ever be given ·in any . , I " 

' ' 

.: .. ~·, 

' l, • II l '. 

",/ .. \ J, 

• J 

! 

. ~\ · .. GI 

.. ~ 

J' 
REF ID:A66639 

plalD yx.t oonmanicatlon • code; or· cipher message Wb.1ch max connect l t in w wa.:r 

with a mas aye previously sent. Ot course,. I need hardly add that a message once 

aent in code or cipher must never be repeated in plain text under a:ny olrcumstances -

there la no exception to th1a rule. The danger .ot .&Uch a procedure la so_obvloua . . 

that lt 1e hard to conceive of aDJ normal th1nkil'lg person doing it.. Yet p let me tell • , r • 

you of an actual instance. 

(Case 2) 0, .J o.e..,;:.\.. ' ~A~c.o J..... ~ ~ ~~ 

It seems hard.11 necessary. to say that the insertion of plain text in code 

. . or cipher test U so highly da.:ngerous that it- Should never be done utlder any ciroumetanoea. Of course it 1s possible that in a long report~ only one or tWo Fragraphs 

might be secret, in which caae, the rest of the report could be sent in plain text, ' . 

prOVidlng that the plain text matter Will. f?:1Ve no Ollie Whatever: to the encoded or 

enclphered matter. However, the best pl~1ot all would be to make them separate, . . 

The 1naert1o:n ot anJ signs, ab'brevla:Uo:ns ~ ~r punctuatlon should be absolutely . . . . . " 

prohibited. This would ·seem obvious bUt let .me t~l .you of an instance .1~ Which t~e 

insertion ot an abbrev!$t.lon lead to the solution of a message. '(Case 3). 

The plain text and cod• or cipher messages Should .. never appe~r on the 

. , 

same aheet of pa.per; in the event of the· loss· of the papers or t~elr ooptur~ • there 

would be lea~ likelihood of the two being compared. As 'soon as a· measage·haa been 

encoded or decoded~ all the work sheets used in the process must be destroyed by 

burning tn atr1ct accorda.noe'.wlth the regulations set for~h. ;:_ ~~~~- ~~-~-~~--_cL,Jt.­

oodo ro~ 1a th.e inost ~erous article ~t ~urniture in it.~ If ~t ·is necessary to 

keep an exact cow ot the plain text, the same ahoul~ be kept μi the ·coding room and 

·. ' . guarded with as much secrecy and care as the code itself. ·Where a pleili text copy ot . •,• . 

1ihe message must be furnished to departments Whose Illes are not ·s~oret I the plain . . . 

. . text must be carefully para.phrased. . ... 

' I 

~e work of paraphrasing· requ.lree considerable skill. and prao .. 1~e .,\and 

. ' in the case ot matters ot very great importance, the para.phrasing Should; ·be.\done or . ' . . \ 

auperv~sed by the higher ottioers. .:::;l;;;;R.-a;;,;:l:;,:;l-....;:;;c.;:::a.::..se::.;s::....::th=e-paa;;;:::;.;r:.;:a .... p-=hr=-a=-· a=-1::;.:;·ns-....· _mu==-1t::....:::b;.::e._d.:.:O;.::n:;;:&;....:bo:::e;:.fo~r::..:.e· 'I 

the message leaves the opdW room. 

To ~ ot you .. ,Parapbraslllg a measage is more or lesa UDrf'amilia~\, and 

lt might be advisable tor me to give an illustration. I'hrill do no good t~ ohange 

merely the order ot·a word or two in ea.Ch· sentence.· The entire torm of 'the ntessa~ 

; ', ' 

must undergo the ohange. 1'he mesl:18-ge should be altered by the subs't1~~.1on ot \'._ '"· 
REF ID:A66639 

W.S• 

QDO•s., the .e~s..boratlon of phrases-, th_e ch~ from active to passive voice and 

. ' 

vice versa.• eta. all of Which ahOuld be without eas~tla~ cha~a. in the ~1gn1f'icanoe 

ot the message. .1'han the sente2l.ces may be shifted about so that the t~l result . . . 

bears ver1 little resemblance to the original form ot the- measage, .The best way ot 

approaching the task la'tlr.st to read the meisage over very oareta.111 iD order to . ' . 

get a clear ··tdea of its meaning. , Once that ·1a done the principal ideas: are to be 

expreasad'in:a torm aa different as possible from the orlglnal,"tlthout material . ' 

alteration in.the intent Of the meaaa.ge. lCase 4) 

With all these pr&cautlons, lt hardly seems naces&8l'J' ~o remind you that 

encoded or enclphe~edmeasagea must u9ver be tiled with their .equivalent plain text. 

I have personal knowledge of au.ch an instance~ 

All ~a preaautiona that 1 haye mentioned. ·so tar are of @.:.·general nature, 

. . 

'but 1 must add one mor•: PYER SEND COD~ OR oinma MESSAGES BY WI:gx.ESS OR BY Alff 

. . . ms SUSOEP'l'IJ!LE 01 Ea.SY lll!TEl!CEPTION WHEN A MORE, SliXlRET MEANS "IS aVAII.dBLE AND - t 

WHEI. 'ME BATTER DOES J!OT REQUIRE mEDIATE AHENTIOE. If there ~e rep.arts upon 

matters ot no particular importance at the moment,··the7 might better be sent by 

courier or th.rough the regular cha.JUiela rather than ·~·ransm1tt1ng ,them 'by wireless. . •' . 

The reason ~or this is ~hat the greater the amount of traffic an enemy can intercept, 

the greater bis o:hano·es' for brealtJ,ng ·into the code .• · Purthermo~e • the ehemy may in 

certain oases.gain valuable lntorma.tion merely ·from the number ot meas~•& sont .and I ' 

tbelr length, wlthou.t being ln a position to read a single one of .them.· . That applies 

more to m111ta.i7 afta.1rs, I suppose,. thfm naval. It may be int.ereatlng to you to 

learn a few tacts bearing upon this phase of the que~tlon by gl~1ng you· an instance 

from tho ,i-eo~t .w~r. ~ 1o ~ ..,.r- ~\. ~ ~\ . 

tcaae5J A;t,.~~c?~·~· . l should think that 1t would be wise to regal.ate the a.mount ot traffic 

during an actual state ot war so that the en91D1' can draw no oonclu~io:De' .from the 

number ot messages. In regulating the amount ot trat.f'ia,. routine messa.g&a sueh 

' \ 

~a da.ilJ or wee* reports,, especially it they are ot set forms; must be stn'ti \ ' ' by other means~ They are highl7 dangerous because of the similarities of c~nten~a. . ' 

1. "\ 

.. There is a method .ot breaking tnto a code• cal~ed the Analogy Method 1 ~fch ma.~ee , , \ \ 

\' \ uso of just such messages. 

(Oaas 6) 

The sei;iclitlg ot short messages should ~e avoided becauee the nature ot 

such me•aagea ls. rather limited and lt they are apt to ba very trequent'they 

. '• 

. ~ 

· .. 

' \' .,\ 

" \ 
REF ID :A66639· 

constitute tavorite polnta o.f attack. tease~.) 

Oxle ny to eliminate _th1s 4allger 1s to ~ good use o:t the durmay groups; 

but their use must be jwlioious. ( Oaie a.)-

The use ot dmrmles 11 to be emphasised, eapeo:t.allr in ph~~a.as or'. between ' . .. 

words likely to be repea·tad several times ln the same meaaagari OI" ln several messages. ' . 

The;v must be aployecl 1n the speU lng of such words as a.re not preeent lil the· code • 

.Avoid the use ot word.a and phra~ea not· 1n the aode when other wrds or . ' . . 

E)lraaes with the same signlticanae are Rresent, )ecause t~ la· absolutely> necessary to • ' ' -~ tlO\' ; 

avoid spelling out_.word& or phrases al ma.oh as· possible.· ~ere··a.~~dy~tages in 

spel~lng out such words When 1t is unnecesae.17 and m<?reover suoh procedura- opens the ' ' 

way tor an s.t~ok. bf _the enemy 'because it bas been found that·the apelli;pg groups in . ~ 

a code constitute ~weakest slemente. 'e# Mis::: u. 1'he fewer spelling groups used 

' ' 

the more secui:e will 'be the code. . It may· eo'U;lld. i"a.r .. tetched to you if' I tell you that 

the code·ma.~,atter a caretal study of the text of.a ~onsiderable n'QJ!lber of massage~, . . . . ~ 

1e able to determine. tor t~~ majority. of th~ groups that appear·, ~loh ~s~. 

represent punctuation1 \111hich, spelling groups a which, militaey or naval· units; etc. ' ' ' 

In the oawe of the apeli·liig groups after a sufficient number ot them have been . . .. '. ... . ~ .. . . 

classl.f'ied as being spelling groups, there is invoived only a more or less sbllple 

case of subatltutlon cipher. Onoa a few ot the spelling groups have- bean solved 

a gr~t break baa been made ~to ·th~ code •. Remem~er then; use the apelllng groups ' . ' ' 

aa little as possible.,. and Whan they must be used exerclse oaution. and use your . . 

best Judsment. 

. Another. rule t Which seems- almost too obvious to ment-lon f is ·that all 

. ' . operations .applyl.ng to 'the system of eno'iphe_rlng' or encoding. must be completed, 

' . lt there ar.e t~ee opera.Uona :ia.eces-s'aey, lt would be highly daJJge.rous to.' leave off ' . 

One Of" them, Bay the final.' Olle• 'l knOW Of two. caae$l:n WhiOh an eno.lpber~r f e.lther ' • ~ ' ' ' ' ' r I .. :' 

through ca.releaeneas or a tool1Bh ·belief t~t one operation wa.·a ~tficient .. left ' .. I ' 1 ' ' 

• • I • • ' ' 

ott the final ·O~eration ln enolphering. The results werel?!OJ1$ disastrous-. ' ' ' I I 

A.ft~r. ~.consideration ·of the"·general prlnolplea and rules 'th~t ap~j,y<t~, the 

' ' ' \. ' 

preparation ot mespages t we come t-o a discusa lon of. some special and d~ta.ii'.ed ?ea.tur,s. 

I ~~!Ji>OS~ •· it ~ were a~ked What is the most important ot the ·+~r ~ea w,ith ·. : • • ,'lo t 

• ' ; I ' ' : & ', regard to ·au ~ryptographic :p~ooesses; tor the purpose a of ma.king them secur~, 1· ."' ~ ' I • ' • ~ <' 

ahouid say'tlu\i.t i~ ls the principle ot random selection or use ~t anythl~g pe~taini~. 

•. 

to the sy~tem~ I ~o ~ot. know ~ow to impress upon you the lmportanc.~: ot this} ) ·-...._"'-

.r --~t 

' ,\ 

' \ 

/~~ •' 
REF !D:A66639 

prillciple. One of the factors Which moat often lafl.t. to a first break into tJ;ie 

· German systems• was the methodioalneH of the German mlnd.. The typical German 

mind 1s so fila.sctiinat.edwith the ldea ot doing everything systemically apd in 

a.ocorda.nce_ with a set form that everythlng he does must be done .. ~~1.H).J'OJ.~('t:OJ.311st~:Q:r;.,then. 

When he baa once adopted a system lie never departs from· it Unless it ~s ~peclt1cally 

called to his attention. lt was his slavish adherence to.set forms that most often 

gave the leading oluaa. And it he· waa told that he must vary his procedure• he 

varied it aoaord1ng .. ~ to a a1starnU. 

I muat oo!U,'esa;however, that our own forces :were not a grea~ d~l· better I ' I I 1' 

111. this respect than t~e German. Time and aga In we ·a8J.led attent~on to the flagrant 

violations ot the rules by men in ·thh regiment or that regiment. But the ae~ioueneBl!I 

ot the viola.1i1ons, I am ao~ry to say, was little appreciated by the superior officers 

ot the men :;mo were guilty. You know how dilt1oult it ia to get action on things 

. . like this through the usual channels. The men 1n act 1011. think that there are a lot ot 

.. old togi&a ~ack at hea~rtere, Who have nothing to do but a~se themselves getting 

up a lot' ot ~tool .r'lilea and regala.tions" with 'flhioh to pester them, They say to 

themselves "How the devil 0821 the e~ get anyt~fqlg out of a code message that is . . . . . 

noth~.but a jumble of letters? If this tilng war~ not sate they would not give it 

_;"~';, 

to ua".. lt mq be that it la pyach?logioally impossible to make· most men realize."the . . . . . .. 

seriousness ot the hundred a~d one m1nuta precautiona that must ~e oba~rted,.e:acept - , 

by actually letting them see how solutions are achieved trom the most slender of 

threads $Dd f~ fetched clues. 

lor example. 1n ~lmoat evel"J ~~de tor secret oommun1oation1alterna.tea or ' , 

varia~ts tor the moat frequently used gr4ups are gi~an. I cannot tell JOU how 

d1tt1cult it is to get operators to use these variants and use them.at random. 

A ayatema~lc aela.ction ot those variant• would be dangerous._. for example:,at .t'irat 

the German ope.rs.tors had the id~a.that it a word, or a spelling group• or a 

punctuation aign ~Qcurred s•veral tlme·a 1z1 a message, the variants war~· to be used 

1n auccaeaion~ the first on• the tirst time 1 t was used, the second the ~eoond time, 

eta, Or lt the group was Ohl.7 us-ed onoe in a message; the first· variant was .to be 

used.· Such:a ptocedure a.a the.latter does not accomplish.the 'purpose tor Which the . ' 

variants are lnteDded. (Case 11) 

Anot~er source ot danger 1s the repeated use ot the same express ion, whether 

it be in the begllmilig, middle• or end ot. message •. I w0nder how many ot you realize 
REF ID:A66639 

-athe clanger ·involved 1n suoh lmpQrtant, parts of a message as the address and SlB11&ture. 

' . 

In· cipher work e.spec1all71 these two parts ot ~ message are ·always the first to be 

attacked. low .tf, aa often happetta, iaesaagaa contain the aama addresses and signaturefJ 

' 

m&Jl7 times• aolution la particularly ea17 ln certain forms ot ciphers. For example• 

one Of .the aatest cj,~~l knQiw op be aolv.t.. lt one ha.a two eur llllM +•~sages. iJ?. 

..e11.r'1AV-t;Lo.o.~"'"' ~ ~ iitUAA-'f ~ . . ·- the same keJ'1\in which 1;h s:t.gna~e is the ama, And recently we ~olved another cipher, . . . 

Which was heralded! ~~~:ri ~ o·ther expe~t•>as being .abiolutely lndeolpherable by taking . . . 

advantage of the tact that. the addresses ot the mes sagas were 1n c lpher too .. even though • t I ' 

I I ' ' ~ 

they were all different. lt is not so much tb,e tact that addresses or signatures are . . . . 

"cbngerol\a as the ~act that the bgginii1Ma pg ends. ot. messages arfl alwags .weak points. 

It ls.Just as dangerous, if not.mor~.S~i to have a more or less set form ~t beginnlllg 

meuagfEj suQh ae "A.clmowledghlg 1our message number ao and so" o~ "Referring to your 

. . message number ~ and ·so" •. 'l'he only guiding point i'1 suah matt&J"S..'.ca.n.,be - avoid all _ I 0 : ' < I \'f • "° I '•\ ' I 9f'• 

aj;'~!:yp.adexpreasloni and _ad.Jlere to no·regular to.rms in doing au:yt)llng 1n arxptographlc 

' . 

The use of panotua.tion 1i1 a code or aypber·maaaage, except Wh.e.te the sense 

would be amb~guoua without it, should be. avoided. 1 should .say that one ot the greatest 

sources of oluea in. our work on the Ge.rman Trench Codes lay 1n the axceaaive use of all 1 

forms of pu.n.a'tuatlon by the GeJ,'IDSD· operators. 

. . There la one. mor.e 9aut1on that I might mention. Never give the ·.en.ezey- a chance 

to make any deductions with reapeat to the contents of any messages if lt :can possibly 

be ~voided. Let us suppose tor example that th$ units o~ a squadron are 1~ maneuvers • 

. A Short meaaage tollowed by a certain maneuver would enable a vigilant enemy to make 

. certain deductions as to the contents of the- massage Which dictated the movamen.t. 

Similarly a mea_e8&'e sent from A to B, followed by a Short message from B to A, 

followed bJ a rep1t1t1on ot the .first message by A Would certainly lndicat.e a request . . . . for re~titlon on the part ot B... Or a long message sent by A, then a short message 

trom B followed by a rep'e_t.i tion of the tlra t meeee.ge from say the thirtieth group 

would·certainl7 indicate a statement trom B to• to the effect that the message was . . . 

intelligible trom the thirtieth group on. All auoh clues must be suppressed. 

l have referred once before to the dangers of abort messages. -A short message 

from A to B follow'4 by a ~onger message from B to A, say w1 thin ten or ti~teen minute_!) 

would indicate that :possibly "question and a.nnert had been exchanged be~en the two 

atatlons.B; watchlDg theae ahort messages the initial groups are apt to be eas~~ solved 
REF ID:A66639 

because quaat1ona cost often begin •1th interrogatives such as ''When" "Where" "BO'fl'I 

or verbs such aa "la" "Are" "Have"· etc. 

'!h~se respona1ble tor .the uae of code, books should regard it aa'part ot 

their dJiti~a .t~ a.end ~ t~ hea~r~ers from time t? time a list of words or phrases 

Wblah ar' not.present hi ~~"cod. and Wh1ah a~e ~aed sufflclentl1 to warrant their 

belng incorporated. In this connect lo~ I ma.1 t•ll you. of the most pecullu anomaly 

ot the G.e.rman trench code• :It bad no worQ. tor cgde book. Consequently,_, -every I • ' • 

reference to it had to be spelled out, Bow it waa the regular practice to notify 

the atatione, after a new code book went into effect, to re~urn the old codes. 

Cona~quently, in the traffic the (l~st dB:y ot the life Of a·nE!\V code one:-0r more 

' . messages could always be found tnstmoting the stations to send back the ·old code books. '• . 

Since the ·word Qode Book bad to be spel.led oμt, the tindi.ng a~d 1olving ot such a . ' 

measage at onoe enabled us to mek8 a great hole into avar:i new code~ If 1 were asked 

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What word 1n all th~ German meaasges ~ve · the most useful clues to soluti-0n, I should 

1 • say 1 t -~ this word "SatzbUchn. Thia went on tor over two years-all tor the lack 1 tive · ot a man with satt~cient in~tifiju ~d regard for his duty to info.rm the proper 

author! ties. (case 12 )· ... 

1 have told j'ou about some o-t the things ·Which helped us 1n our W\>rk on the 

G.erinan codes and ciphers used.on the battle front, a.nd have hinted at succesaes. 

' . Ot our failures, I have ~old you nothing • and t~ey were many. I am· of the opinloh 

and have good reason to suspect. that toward the end ot the war the Germ&n intelligence 

deJ;iartment gave special oours~s of instruct ion 1n the use of code and cipher to the 

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operatol"s 1n charge of transm1tt1ng OOID1lIIUlications. T.b.e rea.aon I suspect t-his ls that 

as time went on the material became ~qreaa1ngl1 ditticult to solve in spi'toe ot our 

oon~inued experience with the material. The en811J¥ evldentl1 came to a realization 

. ' . . "· ,, of the importance of the correct use ot their codes and ciphers and. the result ~s . \ 

that a most r1!1d d•sa1pliae ln communications came to be entorced. The7 .even ~d\\ 

inspectors Whoas duty it was to go from sation to station and correct the e~rora\ t, . . . ' '. \ ' ' 

being committed. One amusl:ng incident 1n this connection ma.y interest you~ .(paae ~2.) 

. . . ' '"'- l\ Th& idea ot having an inspector or a sort of a "Security $8M'io&" 1e '. '1\ . . .. t\ 

'\ 

t1211damentall1' a very excellent one. 2.be security service should be• l_t .seems to m~, 

a branch of the code ·and Signal Section, because .they are in a bette.t' ·position to· \ • ' . . ':'1\ 

realize all '\;he 'mistak&s and pitt~ls and the seriousness of vlolation's of the rule~\~,, ' 

and they should also be able to keep a close watch over all the traffic. SUeh e. \' \ .. 

I. 

department might seem superfluous but I believe that in the ·end it· would more ·than \ · .. ' 

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REF ID:A66639 

pay tor itself. A poor code in the hands of .experts can be used more satel1 than I 

an excellent code in the hands of careless or ignorant operators. Final;.ly, ~ 

·might add that no code or cipher system lmown to me may be -said to be· "fool pr~of".~· 

' ' I • Since the secrecy of operations ls a fundamental prerequisite to success in warfare~· 

it is hardly necessary to point ou~-that the proper training ot the personnel Which 

, ' 

is to' be entrusted with the work of encoding and enciphering, and decoding Dnd , 

deoipherlng ,· is one ot the mo·st important factors in the realm. of milita\ry or naval 

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aeienee ..