This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

A STUDY 

OF 

FRENCH CO:t44UNICATI011S DOCTRINE AND PRACTICE 

9 Apr1.l. l95l. 

ARMED FORCES SECURITY AGENCY 

T()P SEGRET i~1GORN 

Declassified and approved for release by NSA on 06-05-2014 pursuantto E.O. 1352a 
·- ..... This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

9 April 1951 

A Study o:f' French Cammm1 cations Doctrine and Practice 

A. Statement of the Problem. 

In order properly to evaluate the state of eeeurity of French 

cnmnnm1 cations, the history of French cryptographic practice lllllSt be 

studied with the purpose of find1ng answers to tour questions: 

1. Do t.he French knov what constitutes sound CGEEC doctrine? 

2. Do their cryptogrephic practices demonstrate that such 

knowledge is .indeed applied? 

3. Do they supervise cormmm1 cations in order to detect 

compromises and take corrective action? 

4. Do they use cryptographic systems that guarantee adequate 

security? 

Acswers to these questions have been sought :f'rall two sources: 

the actual. published documents of French Cryptogra:pllic Services, and 

the history of French practice aa it is known to AFSA. 

'B. Facts Bearing on the Froblem. and Discoosian. 

This discussion will be concerned primari]J' with the comnnm1 cations 

ot the Arm:r and the Foreisn Ministr.T because 1 t is 1n these two fields 

that there 1e moat current 1Df0?'!!8t1an avail.abl.e. 

l 

ARMED FORCES SECURITY AGENCY 

T()P SEeRE'F A€0RN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

l. Do the French know what ocmstitutes aound. CClrSBX: doctrine! 

The most recent explicit atai.ent of French COM)EC doct.rine 

available is the "Inetructicm. rela'tive ~ 1' organ1.aat1o:a. et au fonctionnement du eervioe de la oorreaponaauce chi.ttree ", issued in l,941 by the 

Secretariat of' State tor War, General. Staff of the A:rtlf3, Deuxi- Bureau. 

Following is a tranelAt1on of Chapter 1, "Cryptographic Secrecy~ o"f 

Section II, "Cl'Y,Ptographic Security". 

"Cryptogra:phic secrecy demands a strict observance of precautionary measures which are eanetimee neglected: certain 1mpru.dencee, 

which seem. at first eight harmless, are capable, indeed, of p:ravel;r 

canpram.1e1Dg the security of cryptographic qstems. 

NO CRYPTOGRAPHIC SlST!M IS PROOF AGAillS'l' CERTAIN 

Maintenance ot the security o'f' crn>tograph.y 1s, ccmsequent.ll', the 

primry condition of 11:.s emplo3Jll8Zlt. It demands on the part of tbe 

cryptographer the rigor01.h1 observance of the rules, called "General 

Security Measures~ 8DUll8l"ated 1n Chapter ll folloving, which a.re the 

result of numerous experiences. 

"It is important then t.b&t in all eche1cms the regul.e.tions 

concerning encryption be ecrupulously obeerred". 

The doctDent cited., other related doclllll.ellta, :Plus f'Ues of' correspondence of the Cryptographic Section of the Any General. Statt, prove 

conclueive]Jr that the French Arm:s, at least during the W'az", recognized 

the need :for ma1ntemmce of cQl!D!lmie&tian security, that 1t expended 

2 

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rep SECRET A€8RN 
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Utmost secrecy fs necessary to prevent drying up this sort of vital intelligence at its source. 

considerable effort 1n the ~s preced1ng the last war in tra1ning 

cryptographers, and thi~t it was amply aware of the ways in which 

co.mmunicat10DB security could be maintained. Pertinent quotations 

:frcm documents an the subject will be found 1n Tab A. 

The on.lJ documentary evidence on Diplanatio doctrine is found in 

the prefaces to certain captured. codes. These prefaces g1 ve instr&lCtifJDl 

tor the use of the eyst.em.1 and also set forth some general aecuri ty rulee. 

These rules indicate that the Foreisn Ministry cryptographers, too, vere 

awe.re of the dangers of poor C~ practice and tried to instruct the 

users of systems 1n ways to avoid camp:ranieing their seeur1 ty. 

A:tm3, l\Ta.v.y, and DiplaDatie doct.nne are seneral.ly the same an me.tters 

like physical securit.y, avoidance of compranise by pla1n-text reference 

to code messages, need for pa.raphraa1ng when cammunicatmg code text to 

a third person, and wrying of 1Dd1catore in enciphered code telegrams. 

EO 3 :3(h)(2) I I PL 86~36/50 use 3605 offer sutt1c1ent evidence of the f'act that 

the la.we of CC!4S:EC are lmown to t.be autbori ties. Aa deduced frail these 

.__ ___ ..... I the French rulee are very s1m1Jar to those of the UoS. Army. 

Most of the rules are e.pparentJ..y lmown, also, ill at least some quarters 

of the Diplomatic service. For eDmple, the principle that a. giv~~l6~i~~~~ use 3605 

system ehoul.d be used far correspondence or a certain c:lass1f1cat1on 

is not unknown. 

3 

ARMED FORCES SECURITY AGENCY 

T8P SE€RET A€8RN 
T () P -4S E etl i!+~ A.~f.2 () R N~o 3.3(h)(2) PL\86-36/50 USC 3605 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

While there are DBll1 e1milarit1es 1n ltrllq, Jfavy a.ud Foreign Mtnistr.1 

doctrine With respect to cryptographic practice, there are certain 

d1:f'f'erences, scae of which appear traceable to mere lack of a spec1f'1c 

doctrine an the Jl&l"t of the Foreip M1n1et:&7. 

ARMED FOR<is SECURITY AGENCY 

'P()P SEeRET A69IlN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

'Jfhere is noted one major doctrinal difference: the Foreisn Ministry 

allows the use of imenciphered code. Furthermore, although same highly 

classified ~odes are acoc:mpanied by the wa.ming that they must never be 

used unenciphered, others have been o1'f'1c1ally used both enci:phered and 

tm.enciphered, thus affording an excellent opening f'or cryptaml,ytic 

study.. The ~·s position, as deduced fran. severe.J. statements 1n 

instructional documents, ie that the originator decides vhether a tele--

gram is to be enciphered or not. It it is to be enciphered, however, 

"Simple enciphermant is, 1n senera.J., illsuff1cient to insure the security 

ot the texts". Plain codes, the doctrine rtme, are eusoept1blo of 

anal.3sis 1 especially if Yide]J used, and :f'tlrther.more 1 codes can be 

secretly photogroaphed. Therefore, "all radio-telegrams must be in 

enciphered code. Ii; 1s abao1ut.e]Jr forbidden to se.nd radio-telegrams in 

unencipbered. code." As a result of ~ appllc9.t1on of' theee opposite 

doctrines, there is no case known of A:ttq use of' plain code, wheree.s 

EO 3.3(h)(2) Arrrzy doct.rine recognizes the problem of repet1tic:n of stereotyped 

PL 86-36/50 USC 3605 

expressions (eepeo1a.11J" at beg3nn1ngs and ends of messages) a.ud v.rgee 

the uee of null.e and var1at4.on in pl.a.cement of internal numbers, 

ad.dresses, messaee references, etc. Dipl.OUBtio awareness of thia problem, 

,__ _____________ l1a .J.1lllited t.o the problem of stereotypes at 

the breaks in messe.se pe.rta. 

Army end Navy instructions urge the systemat.ie uae of var1a.n:ts vhe1·e 

they exist; no Diplomatic mention of t.his point is fo1.mcL 

8 

ARMED FORCES SECURITY AGENCY 

rroP SE6RET ACORN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

"Never s&nd the same text in two telegrams, one in el.ear and the 

other 1n code or one encrypted vi th one code end the ct.her vi th another 

code, or even with another key." This law is laid down in the "Inetruc;!;.-

ti<m Secrete du 3 fm1ar 1936 relative ls. l'orsan!sation et au f'onctionne-

,, ~ 

:ment du service de la COITespondamce Chittree d8Ds l.'.Anlee en temps de 

paiz et an temps de guerre" issued by the Cryptographic Section o~ the 

Army General Staff. It is added tbat, where neceasa.ry, the same 

eubeta.n.ce, paraphrased and otherwise altered, 'llJll:3 be sent in tvo systems. 

EO 3.3(h)(2) The same rule can not be found in 8ZJY Foreigo. Ministry instructions PL 86-36/50 use 3605 

althoush the obvious ban an sending the aaae text 1n code and in cl.ear 

seems to be implied I ~i ted 

above. There is no evidence, however, either in writing or practice of 

the existence o:f a ban against repeat!ns the B8lil8 text 1n two different 

codes. 

2. Do French gzptoera.@ic practices demonstrate that their 

lmowl.e<ige of sound doctrine 1e &Ji>plled? 

In the yea:ra since 1941, the French bave been notor1ousJ..y lax 

in their cryptogr:oaphic practices. This statement ''.\i:·l>liee especially to 

the Foreign Min1stry, but the indictment of the M1li tary serrtcea can 

be only slightly leas strong. Whatever real security is enJoyed by 

French e-aamnmoa.t10DS reeulte d1rectly' trcm the use of a tew inherently 

good systems. Short of physical loss, it is d1i':f1eu1t to caa._prom.1.se 

completely a true one-til'ILe pad. Eut if' the system 1tael.f 1e at all 

6 

ARMED FORCES SECURITY AGENCY 

TOP SE€RET i\G9RN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

vulnerable, the French can almost be counted upan to endanger it by 

violating t.b.e most important rules of C<IEEC. 

French v1ola.t1CllD8 or security fall under three hea.d1ngs. 

(l) :1mproper constrl1Ct1an o:r system, (2) improper compoeiti<m. of' cryptograms (3) failure to obeene the rules asa1net encipbe:r:ment of' the emne 

text 1n 'bro &y11tems. 

A few e.m111;plea of ee.ch kind of violation vill euff'ice to illUBtrate 

the case: 

(1) !:m.IJroper C01l8tru.ct1an. 

(a) Both one .. part and 2-part codes are re-generated one f'ran 

another by sim.ple re-pagJnation and re-llneatian. 

(b) Additive key is systanatically generated. 

( c) 'l'he same ke3' 1s used to encipher several codes e (The 

krrD:f Jma been especially derelict 1D this respect). 

Under this head misb.t also be :mentioned the fact that it haa 

orten happened that the ccmp1lat1on a1: thori ties have issued instructions 

tor use of systems 1n au attempt to ilnprove sec'Ul"itY., only to have their 

procedure provide new vea.laleeeee tor the enal.Jrst to exploit. Such a 

case was the 1.matruction that the groups for 1nd.1cating the parts of a 

muJ.tlpart :messase 086Se to appear in clear at the end or the part, and 

be enciphered somevhere in the bod3' of' the text. At the time this 

change was made, 1t took three code groups to :1.ndicate the part. Many 

Ef 3.3(h)(2) 

'------------------------------------'p 86-36/50 USC 3605 

ARMED FORCES SECURITY AGENCY 

T8P SE€RET J\€8RN 
I 

'P()P~E~~~ J:\~8RN This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

(2) Improper Canposit.ion. 

(a) Stereotyped begjnn1nsn are regularl;y employed. 

(b) :Plain-text addresses are often repeated, enciphered, 

1n the text. 

(c) When var18nts a.re available, certain ones a:t"e over-uaed. 

(3) Be-encipherment 

or all rules of security' this is possib]J the moat important. 

It is also the one that has been violated the .most flagrantJ3 and With 

"the most dire resu1ts. The Foreisn M1niat17 is by all odds th& chief 

ottender on this score, although the .Military are by no means free of 

guilt. Re-enciphennenta U8UAl.l.y CCI.Ile about. tor one of tvo reasons. 

B EO 3.3(h)(2) 

ARMED FORCES SECURITY AGENCY PL 86-36/50 USC 3605 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

3. ~ the French su:pery1se cammn1cations in order to detect 

ccmpranisea and take corrective a.ction? 

There is sane attempt to catch errors end see that 'they are not 

repeated, but it can not be seen that this surveillance 1s either 

EO 3.3(h)(2) 

PL 86"36/50 USC 3605 syete!!la.tic, consistent or ef'fective. 

The violations tba.t are caught o.nd reported a.re generally of a 

seccmdary importance. 

9 

ARMED FORCES SECURITY AGENCY 

'F()P SECllE'F Pi:C()llN 
TOPr8EeR.ET2

X2ROR"NEQ33(h)(2) 

This sheet of paper and all of its contents must be safeguarded with the greatest caitt?L 86-36/50 USC 3605 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

Phyaiea.l. ccm,P1'Clldsee ot military e1'Stems have been re.Ported 

frc:m time to t.ime and the necessary action has been taken. { 

But most canprCIDiaes reeult1.ng f'rom. blunders in caomnm1cat1on 

EO 3.3(h)(2) 

seem. never to be caUS}lt. 'l'h.ere have been few 1nstancee recently of PL 86-36/50 USC 3605 

mill tary systems so red. but the hiatOrJ" of 1947 and 1948 is full 

10 

ARMED FORCES SECURITY AGENCY 

TOP SECRE'F t\€0RN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source.pl 86-36/50 USC 3605 

The concl.usion can be onl1" that the security manitoriDe; system 

of the French - it a .fomal. one exists - ie not doing 1 ta job. 

EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

4. Do the French use adeg,uatetz secure cyptoe;re:phic qetemsT 

11 

ARMED FORCES SECURITY AGENCY 

TOP SECRE'F ACORN 
' IC r::; I '1 ~ Eo 3.3(h)(2) 

This sheet of paper and all of its contents must be safeguarded with the greatest care. PL 86-36/50 USC 3605 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

CONCIDSIONS 

The Fl'ench Cryptographic Senicee,, both Diplanatic and Millta.?7, 

!!J1J.Y be fairly presumed to understand the rules of coranm1cat1ons 

security. However, the rules are too often violated by the operating 

persmme1 and the errors too o:ften go mmoticed by the authorit1eso 

These circumstancee, coupled with the fact that most traffic ia sent in 

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T()P SECREr AC0RN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

systemsL.l ___________ _.luormvhlchuaremveakentJC'.i.ubyu~j,~~ 

methods of use, result 1n a ccmmm1cat1on operation in which the 

elements of 1Dsecur1ty cans1derably outweigh those of security. 

13 

ARMED FORCES SECURITY AGENCY 

+OP SEGRE':£ A60RN 

EO 3.3(h)(2) 

PL 86-36/50 USC 3605 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

TAB A 

Quotations .f'ran Military Statements 0£ Crypto-Security Doctrine 

I. Source. ".Instruction eur lee eomU t1 ans d 'emplo1 du oh1:f"f're n, 3 Marcil 

1940. Ccmmendan.ent en Chef' des Forces Aerienne, Etat -

Me.Jor General. 

Chapter II, 7. 

Acy encrnrted meseage sent by radio-telegraph o-r radio-telephane 

can be 1ntercepteii by monitor stations and thus constitute an element for 

study handed over to the en.eim_y ClJ'Pta.nal,ytic Services. 

The results that they can expect fran their labors ue, in ge.nere.l., 

:propcrtional to the number ot documents available to them. 

Chapter III, 8. 

A cryptographic system. mB:J" be eamprcmieed.: 

Directly: 

When the methods of encr;yption became lmown to the enem_y as a 

reeuit of theft of a document or a machine, loes or photographing o:f 

codes or keys, es:p1onnase, 1nd1scret1ons of crnitographic :perscmnel 

concerning method.a in use, etc. (It isn't necessary that a document 

d1sr.oppear for it to be ccmpram1aed.) 

Indirectly: 

As the result of cryptographic etudiea that the enemy may 

undertake on encrn>ted :messages which have 1'a.ll.en into bis hands 

These studies can be considerably .facill tated by: 

14 

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camnand; 

Technical errors by the ancryptor. 

The wealaless of the methods Ellll>loyed. 

Abuse of cryptoe;ioaphy, especially in lO"vrer echelons of the 

•••• 

Cross-checking resulting f'ran. i.Ddiscretions by our services, etc. 

Chapter III, 24. 

It ie absolutely f'orb1dden to :m1 x elem- and cipher in the same 

:message. 

Chapter Ill., 25. 

It ie reeamnended that one avoid enciphering identical texts by 

means of different cod.ea • 

15 

ARMED FORCES SECURITY AGENCY 

~()P SEGRE1? l'io:EJ9RN 
rep ~E61DFDDJA52,&?lf2!8RN 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

II. Source. ".Instruction relative 'a l 'organ.1.sa.tion et a.u fonctionne-

:ment du service de la eorreepondance chiffree, Iere Partie, 

Memento du Chif't'reur", Secretariat d 1Etat a le. Guerre, 

EMA, Detu:i~ :Bureau, 1941. n. 

The present Memento annuls and replaces the "Notice sur lea Proc8de's 

de Ch1ff'rement dene leEJ Peti tee Uni teen of 15 November 1929. 

Part II Chapter II, ~~ Measures !?! Secur1 tz 

1. Use of Cr;yptogre.;phl 

J!hcryptment ie: to be used only in cases of necesai ty. 

It is not to be uead if there are no serious disadv~te.gea to 

transmitti.Ilg tho tc1egram 1n clear, or i:f the iD.formation to be sent or 

to be received can stand the delays of transmission by ord.inary mail. 

It is up to the a.U"!j],or1ty eend1ng the telegram to decide 

whether 1 ·11 is to be encrypted or not. a 

Do not forget that indiscretion concerning a telegram the 

cont.enta of which present only a relative importance can have repercuseions with respect to more important telesra.me. 

Experience hs.e demonstrated that it was relatively easy to 

procure texts of code telegrams, even when they pass only over national 

l.ines; it is therefore indispensable to take the precautions prescribed 

in the :present ~ent& even when the carmmn1 cations persmmel is above 

any- suspicion. 

a. The "Instruction Secrete du 3 rJ'vrier 1936 relative ~ l worganisation 

et au fonctionne.ment du service de la correaponda.nce ch1f.f'r6e dans l.'Arme"e 

en temps de pa.ix et en tempo de guerre ", whose section on :· .r3J;tograpbic 

security is for the :most part identical to this one, iDSerte the following 

paragraph at this point~ "As a rule, correspondence t....-an.emitted on French 

lines or going by French stations will be encoded by simple code; variants 

w1l.l be provided in order to increase the security of this coding :procedure (cbange of codebook, clJanse of encoding)." 

16 

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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

2. Code Room 

Let no unqualified ~arson enter the rooms where encrypting 

takes place, at any rate while encrypting is going on. Do not encrypt 

in a rccm where there are non~French persons, whoever they may bt:, and 

do not install the Cryptographic Service 1n an office to which foreigners 

regularly have access. 

Unless absolutely 1mposs1bl.e, use only off!~ars 1n encrypt• 

1ng and decrypting; do not entrust cryptographic operations and cryptographir. documents to i>ereonnel which ie constantly changing, ie little 

or not known by the head of the Se2vlce, or doee not 1.nspire absolute 

confidence 1n him. 

4. Se.temw,rding of Documents 

All equipment and documents relative to encry:pted corree• 

ponfence mu.st. be preserved with the greatest care in a secure place, 

insofar as possible in solid pieces of furniture, provided with secret 

locks. 

Do not let the codebooks be aeen by persona who do not nave ~ 

use them. Their dimensions, 1n fact, would give indications on their 

structure and the size of their vocabulary. The challging of a code• 

book, revealed by the cbange in color of the cover,ia a valuable 

indication for 'IJDauthorized persons. Same preoaut10DB, or course, tor 

aecret L"'lfltructions and papers which .bave served 1n the cncryptment. 

Open the cipher machines only for ciphering operationsg 

'!'hen lock them during periods of non-use • Do not leave the machines 

"on key" during their movinsc 

17 

ARMED FORCES SECURITY AGENCY 

~()P SE€RE'F ACSRN 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

Ii' a ma.chine is damaged, never entrust the repair of a :part 

to a non-qualified person ( a civilian worker, for example). 

a 

Request the exchange or the machine for a :machine in eood condition. 

It is st.rictly orbidden to keep information or documents 

conceminB encrypted correspondence on one's person or in personal 

articles o:f' :f'umiture. It ie absolutely forbidden to make oxtracte 

from codebooks under t.he pretext or collecting frequent words. 

Loose sheets are the aoi""t of thing tllat can bocame lost or are in 

danger of being sneaked away more easily than documents. 

5. ~hie Worksheets 

All papers which have served in encrypting and decrypting 

are secret documents, of the same importance as the codebooks and 

:machines themselves. 

These worksheets must be burned (and not on.l,y torn up) 

b 

a.e soon as they as they are no longer use:f'ul.. 

6. Use of the telephone 

Give no infor.m.a.tion by tele:phone relative to cryptographic 

operations or explanations on a cryptogra,Phic system. Everyone has 

had the experience of hearing others in conversation over the telephone. 

It is therefore a very insecure way of corresponding. 

7. Wordine or telegrams. Discretion to be observed. 

It is forbidden &nl'Olle having knowledge of' an encrypted 

telecram to speak of it to a;oy person whomsoever vho ie not qualified 

a. The preceding two po.re.graphs do not appear in the "Instruction Secrete" 

of 1936. 

b. The "Instruction Secr~te 11 o.f 1936 adds the following pare.graph: ''Burn 

the old key as soon as the new one is put into service". 

18. 

ARMED FORCES SECURITY AGENCY 

'FOP SEGR:E'T 1L\:GQR.N 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

to know about 1 t. 

Any indiscret:S.an, however insignificant 1 t '!fAY appear, is 

1n :f'act of such nature M to cam.pramise, sometimes irrem&diab~, the 

secrecy of a docUlllflnt. 

8. Pare.phrasing <>f tele~..2!! 

It 1s .forbidden to reprocuce textually o.nd explicitly an 

encrypted telegram in a report, even :lf it is a secret one. 

When the rece:~pt of e.n encrypted telegram obliges any 

authority whatever to g;_..,e orders or instruct:l.w..a relating to it, or 

to make a communicationn to another Department or to the press, all 

provisions must be made eo that these orders, instructions or communi~ 

cations never permit the reconstruction of the telegram by anyone 

W.omaoever. 

The pe.mphras~.ng of the communications to the press must be 

done vith tho greatest c:are, that ie, the toxt must undergo such changea 

o~ form that, all the aha.dee of meaning being respected, the initial 

wording could not be recogD:i:i:.ed or reconstructed (change the vords, 

especially the beginn1:nga and ends, brine together into a single copy, 

the parts of the same te1egram, etc.) 

Th1e precaution is or capital. importance and the author or the 

cc::mmm1cat1on is accountable if it. is nut. carried out. 

19 

ARMED FORCES SECURITY AGENCY 

TOP SECRET A€0RN 
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Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

Chapter III. Technical Securiy Measures 

1. Ez'aft!na o:f teleffi'8l!l!:1 

CryptanaJ.yets base their work upon repetitions of groups. 

Consequently, bave the authorities who dra:ft the telegrams adopt, i:f 

possible, a restrained style, stripped o~ useless formulas, approaching 

what ia call.ed telegraphic style. 

The Cry:ptocraphic Service does not have the right to change a 

wording unleos it has been e.x:presely authorized to do so by t.he authority 

from which the telegram emanates. But it has the right to J'U"Opose to 

tlla t authority any changes in wording susceptible of avoiding lengthb.ees, 

spell groups, re:petitiollS of groups, in a word, everything tJia.t can 

afford an opening for cryptanalytic study. 

Tho Cryptographic Service is, however, qualified to make 

slight changes in form auch as the tranef'erring of the numbeJ~ and roferences, which the drafters usually pl.ace at the beginning of a telegram, 

a 

to the end. 

2. Encry;ptinB of tele1£8!1S 

(a) Be well acquainted with the cryptographic docunents. Apply 

strictly the cryptographic rules which indicate the way to use them. 

When the encrypting system. chosen involves the use of a codebook_, 

the telegram must be encoded in such a. way as to utilize to the 

fullest the fac111t.1es afforded by that codebook through the use of 

a. This paragraph does not appear in the "Instruction Secr~te" 

of 19.36. 

20 

ARMED FORCES SECURITY AGENCY 

T9P SEGRET AG9RN 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

sentences or expressions which appear in it, and to avoid repetitions 

or spell groups. Thuo several groups are gained in a telegram. 

(b) When a word does not exist in the codebook, spell it out 

in syllables or let.ters which are encoded ew-easiveJ.3. 

Severe.1 CODBocutive words thus encoded by their consecutive 

pa.rte are separated f'ran each other by a null group when thls 

precaution seems necessary for the clarity of the translation. 

Use the group "Separation of' spell groups" if that sroup appears 

in the codebook ••••• 

(c) Encoding of repeated word.a. 

Ii.' a repeated word baa several variants 1n the codebook use 

them in turn. 

Ii: it has no code group and must be spelled by syllables, 

spell it in a different manner ea.ch time it recurs ••••• 

(d) Stereotnied f.onnul.as. 

Avoid the freqv.ent uee o:f set textual formul.aa, called 

atereotypeds 2uch as "I have the honor of reporting to you", 

"in reply to your telegram", etc. 

These formuJ.ae give rise to aeries of groups in which 

repetitions frequently arioe. 

(e) Use of null croups 

To conceal repetitions of groups in the formulas often 

employed. such ao the etorcot.Yl>ed tormul.ae referred to stove, it is 

recommended that they be disguised by the nuJ.l groups. These are 

interspersed among the words or ey1l.ablea or else, in short telegram.a 

21 

ARMED FORCES SECURITY AGENCY 

~9P SE8RE~ i\89RN 
IC r::; I 1 1. 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

Null groups are also advantageously employed under the 

.follov1Jlg conditions: Placed at the beginning or end of an 

encrypted text, they :prevent the cryptanalyst fran maJd.ng 

hypotheses an the beginning or end of t.he telegrmn, hypotheses 

which practi.:·.e o.ften ehov8 to be frui tlees. 

Interspersed between two letters or two syllables which are 

repeated in a spelled word, they hamper the work of the cryptanalysts ••• o. 

Fina11J, used to represent punctuation in :pl.ace of' srour>s 

specially deeigo.e<l for that use, they avoid the repetition of 

those groups. 

(:r) Uee of punctuation and grammatica.l :formu.lae 

Suppress unnecessary articles and conjunctiane 1n the :PI"OCeea 

of encrypting. 

Use :ptm.atua.tie>n and grammatical formulas only 1n case of 

absolute neceeei ty, when their use is indispenea.ble for the und(}r• 

etandiJle of the text. 

The observance of t.heee rules presents t.he d.ouble advantage 

of reducing the length of the teleeram and of avoiding repetitions. 

In general a v-erb 1n the :present tense is given through its 

infinitive, and a pa.at participle after an auxiliary by the 

infinitive. 

. ............................................. . 

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'T()P SEGRE'T AG()RN 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

(i) Never send two telegrams with the same text, either one 1n 

clear and the other in cipher, or one encrypted with one codebook and. the 

other with another codebook, or even with a.nother key. If a telegra.n1 ie 

intended for two autho:r·itiee who do not have the same materials for 

corresponding, 1ntroduc:e null groups at beginning and end. The length 

can be cha.need by introducing pre1meitlone and articles, and by encocling 

1n separate words the formulas which appear ready made 1n the codebook, 

or a.gain by dividing the two telegrams into parts 1n an altogether 

different way. 

3. D1v1dl.ng of telesrm}!B 

When the draft of a. telegram ie very long or when, because of 

many null groups, the number of groups must be increased, it ie advisable 

to divide tba.t telegram into several distinct tale~ •••• ". 

Ea.ch of the pa.rte must then be encry:pted by metana of a different 

key if the encrypting system permits.a. 

a.9 Thie 1e followed in the "Inetruction Secreten of' 1936 by; 

"4. Precaution to be observed in the use of radio. 

"The 1ntensIVe"uoe of radi'O; an-iliS'ecure means of transmission, 

imposes an even stricter discipline in tJ.~ matter of encrypt~ in that, 

since the waves can be :lntercepted by ~ unauthorized peraon, the 1.n:rorrne.tion ent.rusted to rad.l.otelegi."apny can be ex;pl.oi ted.. by :roreign intelligence services. 

"Coneequently, 1 t is important to a.pplY strictl.y all the regul.a-

·t1one on the subject of precautions to be taken: 

•a. To preserve the eer.ret nature o-r all. the cryptographic 

documents,; 

''b. To let thaee documents be used cnly by absolutely qualified 

:persons, as a ru.J.e o:fficere, who are alone responsible for the doclllllents 

which are entrusted to t.hem (Codee and Methods of using them.). 

"All radio-telegrams must be superenciphered. It ie abeolut1:;,ly 

:forbidden to send radio .. tele~.JDS in unenc!:phered code." 

ARMED FORCES SECURITY AGENCY 

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TOPr~E6ft=B~W~·ORN 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

Chapter IV. Er.rore 1 Repetition and Ver1f'1cat1on of Teleqe.ma. 

••i:oot1••••••••••••••••••••••'•oc••••••0-

3. ReJ>l.Y to Vor1f1cat1on Regueste 

AnJ" Ceypto,graphic Service which receives, by encrypted telee;rw:n,, 

a request for veri:f'icat.ion of a ceyptograan enccyx>ted by 1 t, must proceed 

1n the f'ollow1ns manner: 

a. Verify the or1g1nal. encryptment, and, if it is found to be 

correct, send back emctl.y the same encrypted text with the same number, 

without modifications or additiona.; 

b. If the or1,g1Dal. encryptment is incorrect 1 or if you no 

longer have the documeirta necessary tor verification, send a new telegram, modit;ying the word.ing as much as pose1ble, above all the beginning 

and tbe end, and 1ndica·;1ng tbat it is a verification. Nothing in the 

new cryptogram. must recall tbs first one. 

The new ·l-.elegrem. will receive a number dif'.ferent from 

that of' the first. 

Date and M.me will be those o:f the verification, and not 

those of the orislnal t.E·legrm, '·• 

ARMED FORCES SECURITY AGENCY 

~ep SECR:E~ ~1C9R:N 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its sourceEO 3.3(h)(2) 

PL 86-36/50 USC 3605 

1 

ARMED FORCES SECURITY AGENCY 

TOP SECRE~ iAi:69RN 
~()P ~E8WE?'¥5~A~~()RN E03.3(h)(2) 

PL 86-36/50 USC 3605 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

EO. 3.3(h)(2) 

PL 86-36/50 USC 3E 05 

2 

ARMED FORCES SECURITY AGENCY 

rep SECRE'F ACORN 
TOP ~ E CR:E"P f~O RN EQ 3.3(h)(2) 

This sheet of paper and all of its contents must be safeguarded with the greatest care.PL\86-36/50 USC 3605 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

3 

ARMED FORCES SECURITY AGENCY 

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This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. EO 3.3(h)(2) 

PL\86-36/50 USC 3605 

9 April 1951 

.&. 

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TOP SECRET 1\:GORN 
~ ft.~ _L .£1 \-.. EO 3.3(h)(2) 

PL 8.6-36/50 USC 3605 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

TTtmost secrecv is necessary to prevent drying up this sort of vital intelligence at its source. 

\\\\\ 

// 

// 

2 EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

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'F0P SE€RET AeeRN 
3 

ARMED FORCES SECURITY AGENCY 

'PeP SEGRE'P AeeRN 
This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. EO 3.3(h)(2) PL\86-36/50 USC 3605 

9 At>r11 1951 

l 

ARMED FORCES SECURITY AGENCY 

T()P SE€RET A€()RN 
ft _D _I_ ~ '-. EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

This sheet of paper and all of its contents must be safeguarded with the greatest care. 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. 

2 EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

ARMED FORCES SECURITY AGENCY 

+OF SEGRET 1~~GORN 
This sheet of paper and all of its contents must be safeguarded with the greatest care. EO 3.3(h)(2) 

Utmost secrecy is necessary to prevent drying up this sort of vital intelligence at its source. PL \86-36/50 USC 3605 

3 

ARMED FORCES SECURITY AGENCY 

TOP SE€RET A€0RN