AFCIAC: 13/3 

29 August 1949 

MEMORANDUM FOR ..M§MBERS ..Q! AFCIJ.£: 

Subject: Replacement of the Present Combined Cipher Machin.eo 

Enclosure: Draft Memorandum for secretariat, JCEC, 

subject as abov·e a 

lo The enclosure represents a revision of the 

paper AFCIAC: 13/1 dated 16 August 1949> and is circulated 

herewith for telephonic concurrence as a matter of priod.tyo 

2o Attention is invited to the fact that this 

18 

revision ,,·ms made as a result of comments and recommendations · received after AFCIAC 13/1 was circulated for voteo This 

revision makes no substantial chanees ln the position of the 

u .. s .. on the subject matter, and. aside from making editorial 

changes, a few additional facts bearing on the problem have 

been added .. 

cc: Cnptain H., o .. Hansen, USN 

Dr. A() Sinkov 

AFCIAC: lJ/3 

/K{fi 

vC J.~ARL H. D., JONES 

Secretariat, AFCIAC 

PRNC-NCSW-3~6 

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Serial 

NATIONAl~ MILITARY ESTABLISIDAENT 

.(UlMED FORCES SECURITY AGENCY 

Washington 25~ DQCo 

MEMORANDUM FOR SECRETARIAT JOEC: 

Subject: 

Reference: 

En.closure: 

Jteolaoement o'f the Present. Comb.1.ned 

0ipher Machineo 

(a) CECM=940 dated 29 July 1949. 

(A) Draft stafr Study dated 24 Aug1st 194~ 

(Subj: Replacement o:r the Pre~~·en.t Combined Cipher Machine). 

Enclosu~e (A} is forwarded ln respon~e to th~ 

request made in r<iference {a) " 

EARL E o STONE 

Rear Ad.miral 9 U ~So Nav·y 7. 

Direotorll Armed Forces Secmri·ty Agency 

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AUG 24 194-9 

!Qf_ S'HiORE'f U. 8 .. 1fi=E!S .Q!!1! 

REPLA.C:&.JrENT OF THE PRESE:N1r OOMBI~l!!D CIPHER MACHINE -"--'--'-'--"""'-----·--...... -...--~- I! ... • .. - ~· - _.. - I: 

TMJ'R,qBr.:ti:M 

lo To deter.mine the U~Su Position toward the United Kingdom's 

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

(1) there be a full and complete interchange of 

cryptog:r:aphic _principles and policy on a 

reciprocal basiso 

(2) if the U,,So. Chief's of Staff' cann.ot agree to {1) 

above 0 they authorize ·the disclosure of the 

principles of the ECM (SIGABA} so that these 

may be incorporated in a new British Cipher 

Machineo 

FACTS BEARING ON 'J~HE PROBLEM AND DISCUSSION ... ""'..... - • .. IOIP"'. ...,., 

2o 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 ofrer adequate security in the near future., 

Jo In view of the fact that the Royal Navy can only carry one 

mtiOhine in. the smaller ships, the new British machine must be such that; 

it prov:ldes both for British and for Combined British - U o s .. oommunica~ 

tionso This also applies in the UoSo Navy. 

4o Although the CCM if properly used is a highly secure machine~ 

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

ployed in the mach:i.ne are not as secure as is consid.ered desirable for 

highest level U o S. ""' 1T.JL co.m...rnu.rdcatio.nso 

5o If' a complete exchange of crypt~ographic princip1EH3 and policy 

were to take place, the defeat of either nation could expose to compro:mJ. .;If.. 

all cryptographic activity of the otherh 

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6~ If the principles of the EGM became known to any nation whose 

cryptographic systems now permit the obtaining of communication intelli=· 

genca by ·the UoSo 9 that nation could cornmence using the ECliiI for its 

oommunications 8 thereby reducing the effectiveness of our communication 

in.telligence effor-tQ I·-:. is for this reason that the U ,,So services have 

withdrawn the EOM f'rom sensitive areas and replaced it by the present cert:< 

7o several instances .or loss of the CCM by British holders have 

t)ccurredo These indicate that British commands have not provided for 

cipher machines physical security equal to that deemed necessary by the 

UoSa Serviceso 

Be Present UoSo Policy regarding disclosure of the ECM reads~ 

in part 9 as ~ollows: 

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

as secret information to be di ni.lged only to the armed 

forces of the UoS., or to any U.,So citizen 1"'equi1"'ed to possess 

this information in the interests of the United statesp any de= 

tails concerning the ECM=M134C including rotors 9 wiring diagrams, 

keysp keying instructions and operating instructionso If at any 

time either the Army or the Navy considers it necessary to 

deviate in any way from this policy 9 the one shall fully inrorm 

the other of the facts and circumstances and the change in policyv 

if any 9 shall be by joint agreement" rr 

This agreement was jointly approved on 26 June 1942~ at which time the 

Air Force was part of the .Arroyo 

9o The Ar.med Forces of the United s·tates must reserve for 

themselves 9 for reasons of privacy and security~ at least one high= 

level systemo The only such system presently available in sufricient 

quantity is the ECMo 

't'O:P raJORE!' 

!L So ;g:ug ON£Y =2= 
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lOo There is in existence and operation 9 in the UoSo Navy, 

a cipher machine incorporating modification of tb.e COM princip1eso 

... Thi .s machine is ltnown. as the BC:M {CSP 3800} o. The security of tb.e 

BGM has been evaluated as greatly superior to that of the CCM~ and 

as entirely suitable for the highest le;rel communications" 

CONCLUSIONS 

llo It is concluded that: 

an Present UoSo policy does not permit disclosure of the 

principles of the ECM to the United Kingdom and is 

justified in view of U o So experience with British 

physical security practiceso 

ho A modiflcatio.n of present policy is not warranted.,, 

Co Both proposals me.de by the United Kinga.om in RDC 

5/99 of 13 ~uly 1949 should be rejectena 

_£0 The details and principles of the BCM (CSP 3800) should be 

disdlosed to the UoKo 

~o Discussions should be held with the UoKo concerning the 

adoption of the BCM tnr combined use, either in ixs present form or with such modifications as may be agreed · 

upon 9 as a replacement for the existing Combined Cipher 

~COMMEl\T.Qi\ T1.2_ti§ 

12., . It is :recommended that; 

,!o A memorandum substantially as in Appendix "B" be 

forwarded to the British Joint services Missiono 

COORDINATION 

lJ., Coordination with AFCIAC has been ef:rectedo 

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JTIPASECRET EJ~ C L _0 S_JLJUl 

BRITISH JOINT SERV"ICES MISSION 

OFFICES OF 'rIIF. COMBINED CHIEFS OF STAFF 

W.f\..SRINGTON 

RDC 5/99 

REP LA.CEMENT OF THE PRESENT COMBINED 

CYPHER MA.CHINE 

Previous References:= 

RDC 5/87 = 18 May9 1949 

SM=l041=49 6 June 9 1949 

lo The representative of the UoKo Chiefs of Staff' have 

been instructed to put forv1ard~ for consideration by the UoSo Chiefs 

of staff~ the attached mero.orano.um dealing with the replacement of 

the existing Combined cypher machlneo 

2o Commander Burton=Miller of' the UoKo Cypher Policy Board 

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

It is hopedv therefore~ that a very early decision on the attached 

proposals may be given uso 

/s/ R~ Do COLERIDGE Captain~ R., Ilo 

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lJth July, 194~ 

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APPENDIX 

BRITISH JOINT SERVICES MISSION IN WASHINGTON 

REPLACEMENT OF '11HE PRESENT CDNIBINED CYPHER MACHINE 

MEMORANDUM BY REPRESENTATIVES OF 

THE U o Ko CHIEFS OF STAFF 

lq The UoKa 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 System" in paragraph 2 may not hav·e conveyed to the U a S., 

Chiefs of Staff the full purpose of their enquiryo They have there= 

fore asked that certain additional f'act;ors should be brought to the 

notice of the UoSa Chiefs of Staffc 

2~ These factor$ 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 provides 

both for British and. for Combined British = U o So 

communications ; 

(c) The experts of both nations agree that the 

cryptographic princi2les employed in the present 

C. C of\~• are not SU fficiently secure for the Com= 

bined Communications of another emergencyo 

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

interchange of cryptographic princ-iples and policy on a reciprocal 

basiso They are convinced:= 

(a} That only thus can the highest degree of 

security be ensured for vital combined 

UoSo = British communications; 

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

o:r National security- to either Nat.~on., 

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REF I"Q.jJMl,'tJ..60].3 

I OP,_ 5EGREJ 

4-.. If' the U o 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 9 the UoKo Chiefs of Staff propose that the 

UoSo Chiefs of Staff should authorize tb.e disclosure to the U~K .. 

Cryptographers of the principles and details of the EoCoMa so that 

these may be incorporated in the new British machineo 

5o The UoKo· Chiefs of Staf~ point out that unless full 

oollaboration in this field is authorized now, the deve·lopment of 

the British machine may have advanced to the stage where modification 

to ensure secure Combined Communications will not be possibleo 

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REFagiJ;1.i .• 4 ~Q! 3 1ur_SECREJ 

JOINT COMMUNICA.TIONS=ELECTRmrrcs cmJmJ11rrTEE ·- s•- -- --

SECURITY AND CE,!P-:.!Q1~F~ ~A~ 

REP_l.~qE~!iT OF_j''fil!_jp~ COMBINED CI!=>HER MACHI..fil1: 

(Proposed reply to the British Joint services Mlssion) 

lo The U o So Joint Chief':3 of Staff have carefully considered the 

proposals made in RDC 5/99 of 1.3 July 194.9 concerning the replacement o~· 

the existing combined Cipher r,ifacli.in.e 11 and .regrei~ that they are unable 

to agree to either of the proposals,, Full recognition9 however, is 

accorded tile view of the UoIC Chiefs ·or Sta.ff regarding the necessity 

for replacement of the present CCM: for high= level combined communicat.io;_ 

In this regard;i the !L,So .has developedD and has in operation, a machine: 

(BCM) which. is oonsid.ereo. ent.irely satisfactory for such communicationz, 

If the UoKa Chiefs of Staff desire 9 the U,,S., will disclose to the Unite:-' 

Kingdom. the details and cry·ptographlc principles of the BCM, and will 

enter into discussions concerning its a.a.option for combined use and 

concerning the physical security necessary for its proteotiono These 

discussions can commence in Washington et any timec 

Declassified and approved for release by NSA on 11-19-2013 pursuant to E .0. 1352\3 

.A.PPEIIDIX "B n 

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