U. G. Hl"ES GNL¥ 

AFCIAC: 1Ji3 

Subject: 

Enclosure: 

Replacement of the Present Combined Cipher Machineo 

Draft Memorar .. 6.um. for Secretariat, JCEC, 

subject as atovec 

L, '11he enclosure 1·epresents a revision of the 

paper AFCIAC: 13/1 dated 16 _o..ugust 194.9, and is circulated 

herewith for telep"'.on~,c concurrence tiS o. ro.att.3r of priority" 

2o Att.ention is invi tod. to the :fact that ·this 

revision was made as a result of comments and recommendation.a 

received after AFCIAC lJ/l was circulated for voteo This 

revision makes no substantial chanc;es :i.n the position of the 

u .. s .. on the subject matter, anc. aside from raakinr.: editorial 

ohanp,es, a few additional facts bearine on the problem have 

been added. 

cc: Captain Ho Oa Hansen, USU 

Dr.. t>~,. Sinkov 

/ 

, I ~~ / I ,. //;;} A?U2/~_,,/ YvV J.f KARL 

1,~YH. Do JONES 

~ Secretariat, AFCIAC 

Declassified and approved for release by NSA on 11-13-2013 pursuant to E .0. 1352a 

AFCIAC~ lJ/3 

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tT. s::nn am.y --

NATIONAL MILITARY ESTABLism..mNT 

~MED FORCES SECHRITY AGENCY 

Washington 25p D.C. 

DRAFT - .-- -.. -- ..._ 

• 

MEMORANDUM FOR SECRE'I'ARIA'l' J'CEO: 

subject: 

Reference: 

Enclosure: 

1. 

7teplaoerrte11t of' the Present CombJ.ned ~ipher :Maohiineo 

(a) CECM~940 dated ~9 July 1949. 

(A) Dratt Statr study dated. 24 Aug1st 194'.' 

(Subj:'. ReplacemfJat O:~ the Pretent Com ... 

bi.aad bipher Machine). 

Enclosure (A) is rorv1~rded ln respon~e to th~ 

request made in ro:rerence (a) .. 

. . :l!i.A.RL E;, STONE 

. Rear Admiral~ U. So Navy. Direct~r. Armed Fbrces Security Agency 

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AUG 24 1949 

'±'OP SEORI!l'!' Y. s, l!l¥ES ~TL¥ 

REPLACEMENT OF THE PRESEh"T COMBINED CIPHER MACHINFJ. 

~ PRO~LEM 

l. To determine the U.S. Position toward the United Kingdom's 

proposals in RDO 5/99 (attached as appendix A) that: 

(l} there be a full and complete interchange o~ 

cryptographic principles and policy on a 

reoiprocal basiso 

(2) if the U.So Chiefs of Staff cannot agree to (1) 

above. they authorize the disclosure of the 

principles of the l!:CM (SIGABA) ac that these 

may be incorporated in a new British Cipher 

Machine. 

FACTS BEARING ON THE PROBLEM AND DISCUSSION • -- h ...... ...-, 

2o The UoK. Chiefs of Staff have decided that they must replace 

their Main Cypher Ma.chine (Typex) as soon as possible .since they do not 

odnsider that it will offer adequate security in the near future. 

3b In view of the fact that the Royal Navy oan only carry one 

machine in the smaller ships, the.new British machine must be suoh that 

it provides both f'or British an~ for Combined British .. UoS. oommunica"'· 

·tions, This also applies in the U~S. Navy, 

4o Although the COM if properly used is a highly secure .ma.chine, 

the experts of both nations agree that the cryptographic principles em~ 

ployed in the maohine are not as secure as is considered desirable for ~ 

highest level U .. s .... U .K. oo.mmunications~ ~or ~.A..""\~!lv.~(). 

5~ -Iit a comp]..ete exchange Qf~yptographic principles and policy 0 / "'/ t ,// } / .. .) /- . \ // \ / ( .. ,' wer~ to ta pl_aoe. thj' defeg.i-· of eitier nation could e±pose :to compr~~:lj:>e ,< / - /. _/ /· (/ v c, 

~- /11 orypt~ra.phic aoti ~Y' o:t' the otheI!-<- \._/ 

~'G_ ~v- r°"", s:-

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60 If the principles of the EOM became known to any nation whose 

cryptographic systems now permit the obtaining of communicat.ion intelli ... 

gene~ by the UoSo~ that nation could commence using the ECM for its 

aommunioations., .. thereby reducing the effectiveness of our communication 

intelligence effo~to It is for this reason that the UGSo aarvioes have 

withdrawn. the ECM f'rom sensitive areas and replaced it by the present CCMo 

7~ several instances of loss of the CCM by British holders have 

oocurredo These indicate that British commands have not provided for 

oipher machines physical $eour1ty·equal to that deemed necessary by the 

U o So. Serviaeai) 

Bo Present U~So Policy regarding disclosure of the ECM readsp 

in _part~ as f'ollows: 

"The UoSo Army and Navy mutually agree that they will regard 

as aeoret information to be divulged only to the armed 

fOroes of the UaS. or to any UoSo citizen required to possess 

this information in the interests or the United States, any de-. 

tails concerning the ECM=Ml;340 including ro·tors 11 wiring diagrams, 

keyaa keying instructions and operating instructionso If at ant 

time either the Army_ or tha Navy considers it necessary to 

deviate in any way from this policy, the one shall fully inform 

the other of the facts and circumstanoes and the change in policy~ 

if any• shall be by joint agreement.:. 1t .' ~1 PI '[, 

!J 

1f Cf., This agreement was jointly approved on 26 June 1942, at which time the 

A~r F~rge was part of the Army o ~ °+'f~~ ;/d .-0.e_ 1't..0 ~ ~ J~ -:1-cvivz.... -Rov. ~ ·~a..~ ~~; C , 9o·.o ·Th/~rmeO: F~~es/~.f the United st~es must res~ve fo~,'- ~ 

1 

- ,i tllems~lv~~" ·:r~~~f" pr~':.~cy and .eecur~-~*-a_~n least on~ ... high--, ___ _ 

; leve: __ .s~~~emo Th:?y such· .S.[~em presently avallf'.ble in sutt'i~ient -

quantity is the .ECMo 

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10. There is in existence and operation, in the UoSo Navy, 

a cipher machine incorporating modification of the COM principleso 

.,. This machine is known as the BCM (CSP· J800} o The security of the --

BCM has been ~valu~~s~_r_i=o=r_t_o_t=.P~_a_t o:r the ~~d 

as entirely suitable for the highest le'\fel c om.munica ti ons o 

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CONCLUSIONS 

llo It is concluded that: 

b,- ~o . Present UoSa policy does not permit disclosure or the 

principles of the ECM to the United Kingdom and is 

justified in view of UoSo experience with British 

physical security practices. 

C.. bo -.. A modification of present policy is not warrantedo 

(t .. co Both proposals made by the United Kinedom in RDC 

5/99 of 13 July 1949 should be rejectedo 

(-----.., 

' 

v 

do The details and principles or the BCM (CSP J800} should be - disclo~ed to the UoKo 

~" Discussions should be held with the U o Ko cone erning the 

adoption of the BCM f.or combined _us~, either in i...ts pre~ 

sent form or with such modifications as may be agreed 

upon, as a replacement for the existing Combined Cipher 

Machineo 

RECOMMENDATIONS _..,,.,_.~ 

12n It is recommended that: 

,!!o A memorandum substant1ally as in .Appendix rr3rr be 

forwarded to the British Joint services Mission., 

Q.Q£13~ NA ~I ON 

13~ Coordination with AFCIAC has been effectedo 

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ENCLOSURJtl 

BRITISH JOINT SERVICES I..USSION 

OFFICES OF THE COMBINED CHIEFS OF STAFF 

VIASHINGTON 

RDC 5/99 

REPLACEMENT OF Tiill PRESENT CO:MBINED 

CYPHER MACHI11E 

Previous References:-

RDC 5/87 = 18 May~ 1949 

SM=l04lc:.49 · 6 .rune ll 19li-9 

lo The representative of the UaKo Chiefs of' Staff' have 

been instructed to put fOt"Nardp for consideration by the U.So Chiefs 

of staff, the attached memorandum dealing with the replacement of 

the existing Combined cypher machineo 

2~ Commander Burton-Miller of the UaKo Cypher Policy Board 

is now in ;vashington and is fully authorized to discuss this mattero 

It is hoped, thereforev that a very early decision on the attached 

proposals may be given uso 

13th J"uly, 1949 

/s/ Ro D. COLERIDGE 

Captain, RoN .. 

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APPENDIX 

BRITISH JOINT SERVICES MISSION IN WASffINGTON 

REPLACEMENT OF THE PRESENT COMBINED CYPHER MACHINE 

MEMORANDUM BY REPRESENTATIVES OF 

THE tf o 1L "CHIEFS-OF STAFF 

l~ The UoKo Chiefs of Staff have given further consideration 

to the enquiry put forward in RDC 5/87 of the 18th May and are of the 

opinion that the phrase "with a view to improving the present Combined 

Cyphering Systemn in paragraph ·2 may not have conveyed to the UoSo 

Chiefs of Staff the full purpose of their enquiryo They have therefore asked that certain additional factors should be brought to the 

notice of the UoSo Chiefs of Staff o 

2o These factors are:= 

(a) The UoKo Chiefs of Staff have decided that they 

must replace their Main Cypher Machine (Typex) 

as soon as possible since they do not consider 

that it will offer adequate security in the 

near future; 

( b} In view of the fact that the Royal Navy can only 

carry one machine in the smaller ships the 

new British machine must be such that it proi:rides 

both for British and for Combined British ~ UoSo 

communications; 

{c) The experts of both nations agree that the 

cryptographic principles employed in the present 

c.c.M. are not sufficiently secure for the combined Communications of another emergencyo 

3o The UoKo Chiefs of Staff propose a full and complete 

interchange of cryptographic principles and policy on a reciprocal 

basiso They are convinced~= I 

( 

(a} That only thus can the highest degree of 

aecuri ty be enst1red for vital combined 

UoSo - British communications; 

(b) That such an exchange can be made without loss 

of National Security to either Nation9 

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4., If the Uc S;. Chiefs of Staff cannot agree to the proposal 

in paragraph 3 above, and if it is their intention to retain their 

present cypher machine; the UoKo Chiefs of Staff propose th.at the 

Ues~ Chiefs of Staff sfioul~ authorize the disclosure 'to the UQKo 

· Cryptographers of the principles and details of the EaCoM .. so that 

these may be incorporated in the new British machineb 

5o The UoKo Chiefs of Staff point out that unless full 

collaboration in this field is authorized now, the development of 

the British machine may have advanced to the stage where modification 

to ensure secure Combined Communications will not be possibleo 

!1_ Jul~_ 19.Jr.2 

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REPLACm'1ffi:!f: OF._ THE1, j'_gES,E:I1t~-Q,, OI!fill!~.P._-9].J:fIBR ]'.:'fAC.fil]! 

(Proposed reply to the British .Joint Services Missio.u) 

lo The U o So Joint Chief a of Staff have carefully considered tl,f:. 

proposals made in RDC 

the exist:i.ng Combined 

to agree to either of 

5/99 of lJ July 1949 concern:tng the replacement cCipher Ma.ohine f and regrat that they are unable 

the proposa.lso 'Full reoogni ti on» however, is 

accorded the view of the U oIL Ch:i.efs of staff regarding thE: necessity 

for replacement or the present COM for: high~level combined _communicat:l.0.Y\~. 

•.' 

In th.is regardj) ~he U o S" ¥as developed 9 , a_qd has ~n 011eratiotr~- a machi'nc 

(BCM~ (_ v1hich 

o.. 

isl\ 

~~*~ ·d:~~~-:tY-~' po. r-~ eeM 

sat:l.sfe.ctory 

.~:t ~ for Wvt .JJ, 

such 

~. ~ communicationrc , 

If the U,,Ka Chiefs of Staff desi1•e 9 the UoSo will disclose to the Unit'~ 

Kingdom the details and cryptograpl1ic principles of the BCM,. and will 

enter into discussions concerning its adoption for combined use and 

concerning the physical security necessary for its protectiono These 

discussions can commence in Washingto~ at any timea 

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