REF ID:A2437290 • 'feP OrlORB9? 

l) R A F T ....,. ___ __ 

12 September 1949 

REPLACEMENT OF THE PRESENT COMBINED CIPHER MACHINE ill £ 1• _.Ii, ........ -- I bL 41il .......... - =a 414 - :;:;ow 

THE PROBLEM -- a&:-. 

l., To determine t.b.e 'Uc So Poa1t1on toward the United Kingdo·m9 s 

proposals in RDC 5/99 (attached as Appendix "An) that: 

(1) there be a full and complete interchange of 

cryptographic principles and poliey on a 

reciprocal basiso 

(2) if the UoSo Chiefs of Staff cannot agree to (1) 

above 9 they authorize the disclosure of the 

principles and details of the ·ECM (SIGJU3A) so 

that these may be incorporated in a new British 

Cipher Ma.ch.ineo 

FACTS BEARING ON THE PROBLEM AND DISCUSSION - . 

2" Ot the two f'oregoing proposals.I> the first is unacceptableo 

The United States Government adheres to the generally accepted basic 

principle of national sovereignty and security that the means and 

methods which a government employs tor the protection or its own 

communications constitute a private matter not to be shared in toto 

with any other governmento This principle is sound because it is 

impossible to be certain that a former ally will not be someday 

over=run by a common enemy or may even become a ~oe 9 in whioh oase 

a well=rorged weapon may be turned against its originatoro ilS regards 

the ef'feots or such a contingency~ the primary danger in the 

cryptologic field is not that the security of comm.unicationa may 

be destroyed or impaired but that the sources of commun.ie.ation 

intelligence may be dried UPo 

Declassified and approved for release by NSA on 09-29-2013 pursuantto E .0. 1352fl 

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REF ID ~437290 

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Jo Wlth regard to tha second proposalp it ·1s relt that this solu= 

tion to the problem.shouldbe accepted by the United States 9 for the 

following reasons: 

ao In the spring of 1947 there were Joint and Combined 

conrerences on this subject~ At .the Joint conterences the Army 

-... .. representatives ravored disclosure or the ECM principles to the British 

for incorporation in a new CCM but in dererenoe to Navy objections it 

was tinally jointly a.greed not to make such d1sclosureo At the Combined 

oonrerenoea it was decided to initiate studies which might lead to 

improvements in the security ot the CCMo The results or these studies 

have been largely negative~ the only improvements found to be capable 

ot practical embodiment being those inoorporated in a modification or 

the CCM known as the BOM {CSP JSOO)o However~ the 1norease in crypto= 

security a.f'rorded by the BOM over that artorded by the COM is not deemed 

to be or a sufficient degree to warrant UoSa insistence on British 

acceptance of the BCM as a long=term replacement tor the CCMo Moreover~ 

the modifications which would be required in the British Typex machine to 

convert it into a BOM are such that UoSo teohnioians are doubtful that 

they are praotieableo .AlS09 the British have decided that they must 

replace the Typex in any oase and the introduction of a suitable 

replacement would be expensive in terms or time required for researchP 

development 0 and service testingo lt would be to the advantage ot the 

U"S" as well as to the British if such a delay could be av9ided so that 

British equipment suitable also ror Combined ComDl.unications would become 

available at an early date~ 

bo During the Oombined discussions referred to aboveP the 

British indicated that they were aware of the principles of the ECMo 

Thay described them quite accurately and indicated that they considered 

their security to be or the higheat ordero They admitted 9 in factP that 

they had incorporated those cryptographic principles in a rad1oteletype 

cipher machine for their own useo FurthermoreP even as regards the 

engineering know=how which went into the construction of the ECM~ this 

knowledge has been disclosed to the· British9 since they were provided 

2 
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with CSP 1700" a machine Y<-~~ioh is simply an EOM chassis with certain 

of the ECM cryptographic features eliminatedo 

Oo Disclosure Of the ECM to the British and its adoption .. •11 ... 

by them would g1Te the two governments a suitable piece of equipment 

ensuring the highest degree ot seourity tor vital combined UoSo = 

British oomm.unioations on a long-term baaisa 

do Disclosure ot the ECM will not leave the UoSo without 

unique crypto~equipmanto As a matter of raot, a modification of the 

ECM has already bean developed (CSP 2900) an~ is available in quantitYo 

This modit1cation9 which improves the security of the ECMD does so with= 

out in any way impairing its uae as an ordinary ECM or as a COMo By 

means ot a simple switching arrangement it is possible to make the 

CSP 2900 $erve as a device purely tor UoSo oommunicationaD or as an ECM 

tor UoSo ~ British combined eomm.uhioations~ or as a CCMo However~ the 

principles_ of the CSP 2900 would not be disclosed to the British~ 

eo Release o~ the EOM to the British would leave the way 

open to the adoption of the COM for North Atlantic Paot collllllunications 

it such a decision should be found to be necessary in the national 

interesto British - UoSo uee of the EGM would be easily adaptable 

to North .Atlantia Paot communications since the addition or a simple 

already available adapter to either the ECM or the CSP 2900 would 

permit comm.unioat1on with any North Atlantic Paatnation holding the 

COMo In additionD disclosure ot the OCM to the other signatories to 

the North J\.tlantic Pact would not impair the seourity or UaSo - British 

oomm.unioationa since the CCM system would then be reserved ror North 

Atlantic Paot oomm.unioationso 

t~ At the time of the 1947 Combined discussions on this 

subject~ one or the principal UoS9 objections to disclosing the ECM to 

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REF IJ;l.: A2437290 

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'YO:P SMORffi'f 

the British was the increased danger of compromise arising from the 

wider distribution of the equipment if the British Wbre permitted to 

have ito This increased danger is recognized but it is believed that 

the advantages cited above outweigh this objectiono 

go Also at the time or the 1947 Combined discussions there 

were indications that the British did not provide and en~orce 

physical security protective menaures ror their orypto-eqUipment 

equal to those required and entorced b;r the UoSc aerviceso Because 

f 

of this it· was agreed on a Combined level that a prerequiaite to 

further discussions regarding a replacement for the OCM would ba a 

-Combined agreement covering the measures both governments would apply 

in the handling and protection of combined oryptomaterialo Such an 

agreement has b~en concluded and concurred in by both Governments 

{OCB-285~ 11 Oot 1948)0 A review of that document in order to insure 

identity in security regulations applicable to the ECM and an accep~ 

tanoe of suoh changes therein as may be_deemed necessary by the UoS.., 

should be a preliminary to entering upon discussions leading to a. 

tul.l disclosure o:f' the ECM to the Britisho 

CONCLUSIONS ..._~ .. w 

4o It is concluded that: 

ao The first proposal made by the United Kingdom in 

RDC 5/99 ot 13 July 1949 should be rejeatedo 

ba The details or oonstruotion of' the ECii (SIG.A.BA) 

should be disclosed to the UQKo in discussions which should be 

preceded by a review and acceptance by both Governments of identical 

security regulations to insure the physical protection and proper use 

of the equipmento 

4 

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RECOMMENDATIONS wou :be I!- _......, 

5~ It is recommended that: 

e.o A memorandum substantially as in Appendix "B" be 

:forwarded to the British Joint Services Misaiono 

COORDINATIOU 

60 Coord:i.nation with AFCIAC has been eft'eetedo 

9f 0P SESRK'Jl 

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REF :W.:A2437290 

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E N C .J!...O .2.JLB E 

BRITISH cTOINT SERVICES MISSION 

OFFICES OF THE CON!BINED CHIEFS OF STAFF 

WASHINGTON 

RDC 5/99 

REPLACEMENT OF THE PRESENT C O.MBINED 

CYPHER MA.CHINE ----- ·-----·--~---· --

Pre vi 01~~~ferences: -

RDC 5/87 - 18 May$ 1949 SM-1041~49 6 Juce~ 1949 

lo The representative of the U"Ko Chiefs of Staff have 

bee.a. instructed to put forwardsi 'rr:a' consideration by the U o So Chiefs 

of Staff, the attached memorandum dealing with the replacement of 

the existing Combined cypher .machineo 

2o Commander Burton-Miller or the UoKo Cypher Policy Board 

is now in ~\Tashington and is fully authorized ·to d.iscuss this mattero 

It i.s hoped~ therefore$ that a ·;rery early decision on the attached 

proposals may be given uso 

TOP SEGREg;t ----~--

/s/ R, D. COLERIDGE 

Captain, Rt. N., 

APPENDIX nAu 
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APPENDIX: .. 

~RITISH_IOINT SERVICES MISSION IN WASHINGTON 

REPLACEMEN111 OF T~ ~RES~~'.l'. co~ CYPHER N'.A.CHINE 

MEMORANDUM BY REPRESENTATIVES OF 

--· TifE u 0 ,,___ 

K"~""'CTIIEF"s·or STAFF -

lQ The UoK~ Chiefs of staff have given further consideration 

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

opinion that the phrase "with ri viev1 to improving the present Combined 

Cyphering SysternH in paragraph 2 may not have conveyed to the U.,S,, 

Chiefs of Staf'f the full purpose of their enquiryo They have .therefore asked that certain additional factors should be brought to the 

notice of the 1J ., So Chiefs of Staff'~ 

2., These factors e.re:""' 

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

must replace their i!iain 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 on1lr 

carry one machine.in the smaller ships the 

new British machine must be such that it provides 

both for British and for Combined British ~ UoSo 

communications; 

(c) The experts of both nations agree that the 

cryptocraphic R~inc~ employed in the present 

c.c.~. are not ~ufficiently secure for the Combined Com.m.unioat.ions of another emergency o 

3., The U,,Ko Chiefs of Staff propose a full and complete 

interchange of cryptographic principles aud policy on a reciprocal 

basis,, They are con.vinced:.,, 

{a) 1'hat only thus oan the h1ghest degree of 

security be ensured for v.ital combined 

Uof3., - British communications; 

(b} That such an exchanc;e ca.n be nu:i.de without loss 

of National security to either Nation., 

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4n If the UoSo Chiefs of Staff cannot a~ree to the proposal 

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

present cypher machine 9 the UoKo Chiefs of Staff propose that the 

U., So Chiefs of' Staff should authorize the disclosure to the U., K., 

Cryptographers of the principles and details of the EoCoM~ so that 

these muy be incorporated in the new Brit.is.h machine,, 

5n '11he U,.K,. Chiefs Of Staff point out that unless full 

collaboration in this field is authorized now. the development of 

the .British machine may h.uiTe advanced to the stage where modification 

to ensure seoure Combined Communications will not be possibleo 
" TOP SECRET 

REF I~A2437290 

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J'OIID1 COMMUNIG.ATIONS "" ELECTRONICS COMNiITTEE .... 1$ll* <•.~• .._.,caw"' -•...., JI!·-,,_ 

SECURITY AND CRYPTOGRAPHIC PANEL -- m 41 • > cc:;www 

REPLACEJ.IBN:t' O°?. J.'HE l~~S.EN'l'. a·OM§.IHED . C IPUER MA.CH:f~ 

(Proposed reply to the British Joint Services :Mission} 

lo The Uo So Joint Chiefs or St.art.have carefully considered 

the proposals made in RDC 5/99 of 1> July 1949 concerning the 

replaoement of the exlstins Combined Ci»her Maohineo The UoSo Joint 

Chiera or Sta~t regret that they are unable to aooept the proposal 

for a tull and complete interchange or cryptographic prinoiplea 

and policy on a reciprooal basiso HoweverD they are prepared to 

authorize dieousaiona which oan commence in Washington at any time\} 

leading to the disclosure ot the principles of the ECM (SIGABA) 

so that these may be incorporated in a new British Cipher Mnchine~ 

these discussions to be preceded by a review and acceptance by 

both Governments of identical aeour1ty regulations to provide tor 

the physical protection and proper use or the equipmento 

Declassified and approved for release by NSA on 11-19-2013 pursuant to E .0. 1352a