REF ID~436012 

T8P SECRET 9 

AF·sA~ll/ph 

A6~3 

Serial 

'±'OP O:BORH'f 

iI c:: il::tks ~ITT 

NATIONAL MILI~ARY ESTABLISIIMENT 

ARMED FORCES SECURITY AGENCY . WasJ:lington 25, D.C. 

-

DRAFT ___ ....,, 

MEMORANDUM FOR SECRETARIAT JCEG: 

Reference: ,. 

Enclosure: 

1. 

Replacement of the Present Combined 

Cipher Machine. 

(a} CECM-940 rlated 29 July 1949. 

(A) Draft Staff Study dated 15 August 1949 

(Subj: Replacement of the Present Combined Cipher Machine·). 

Enclosure (A) is .fb!'\varded in rqspanse to 

the request made in re:t'erenc(3 (a). 

'f' ffll 3~ 0 ffii:l'±1 

!!i&• gy;s;g QUI Y 

. E. E. STONE 

Rear Admiral, U.SoNavy, Director, Armed Forces .security Agency 

Declassified and approved for release by NSA on 09-20-2013 pursuant to E.O. 1352e 

PRNC-NCSW-34'6 

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'fOP BEtJREi' = U o Bo &Yi!!B .y 

REPLACIDifENT OF THE :PRESENT COMBINED CIPHER MACHINE 

THE PROBLEM 

lo To determine the UaSo position toward the United Kingdom's 

proposals in RDC 5/99 ot 13 July 1949 tor improving the security ot 

Combined oommunicationao 

FACTS BE.ARING ON THE PROBLEM AND DISCUSSION 

2Q The British Chiera of Statt have proposed two possible 

solutions": 

(l) That there be a ~ull and complete interchange ot 

~ryptographic principles and policy on a reciprocal 

basiso 

(2) That it the UoSo Ohiers of Starr cannot agree to (1) 

aboves that they authorize the disclosure or the 

principles of the ECM so that th~remay be incorporated 

in a new British Cipher Machineo 

)o The UoK Chiera ot Starr have decided that they must repla~e 

their Main Cypher Machine (Typex) as soon as possible since they do not 

consider that it will offer adequate security in the near rutureu 

4o In view o-:f the f'aot that the Royal Navy can only carry one 

machine in the smaller ships~ the new British machine must be such that 

it provides both ror British and for Combined British = Uo So @ommuni= 

©ationso This ~a.me point also applies in the UoS~ Navyo 

5o The experts of both nations agree that the cryptographic 

principles employed in the present OoCoMo are not sutrioiently secure 

ror the Combined Communications or another emergencyo 

60 If a complete exchange of cryptographic principles and policy 

were to take place~ the defeat or withdrawal of either nation could 

expose to com.promise all cryptographic activity of the othero 

7a If the principles of the ECM be~ame known to any nation whose 

cryptographic systems now permit the obtaining or communication intelli= 

genee by the UoSo 9 that nation could commence using the EClM :for its 

communioations 0 thereby greatly reducing the e:r:f'e(ltiveness of our 

communication intelligence eftorto 

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

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Uo Oo EYES 0NL'fo 

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. TOP SEGREJEF IJ:92436012 

!0%' OBeRE! • "6 o 0"' EHS ffliLY 

80 There is in existence and operation11 in the Ua s,, Navy<> a 

cipher machine incorporating_modifioation or the CCM principle 9 This 

machine is known as the BOM (CSP=)800)o The security of the ECM has 

been evaluated as greatly superior to that of the CCMo 

9 Q The disclosure to the United Kingdom ~~ the detH.ils of .~the 

BOM will not provide the British with any cryptographic principles which 

they do not already knowa The reverse stepping or the 2nd and 4th rotors 

represents a principle already incorporated by the British in their pr°""' 

posed machines RM26 and RM32o The change in order of progression 

represents a modification or the COM principle which has already been 

specifically requested by the United Kingdomo 

CONCLUSIONS 

10~ It is concluded that: 

~o Both proposals made by the United Kingdom in RDC 5/99 

of lJ July 1949 be rejecteda 

bo The BCM (CSP 3800) be of:fered to ·the British f'or use 

in its present rorm9 or with such modirications as 

may be agreed uponD as a replacement ror the existing 

Combined Cipher Machineo 

RECOMMENDATIONS 

llo It is recommended that: 

,!o A memorandum substantially as ln the Appendix be tor= 

warded to the British Joint Services Missiono 

COORDINATION 

120 Coordination with AFCIAC has been effeetedo 

TI I s b:Yi:~ @IL¥ 
REF 1~436012 

,.,. 

JOINT COMMUNICATIONS - ELEOTH.OlUOS COMMITT~E 

SECURITY AND CRYPTOGRAPHIC PANEL 

REPLACEMENT OF THE PRESENT COMBINED CIPHER MACHINE 

(Proposed reply to the British Joint Servioes Mission) 

lo The UoSo Joint Chiefs of Staff have carefullr considered the 

proposals made in RDC 5/99 of 13 July 1949 cono.erning the replaoement 

of the existing Combined Cipher Machine~ While it has been agreed that 

d1seusaions should take place with a view to improving the present 

system9 the UoSo Joint Chief~· of Staff regret that they cannot agree to 

a rull and complete interchange or cryptographic principles and policy 

on a re~iprocal basis~ nor can they authorize the disclosure of the 

principles and details of the ECMo . . 

· 2o The Uo So has developsdv and has in operationP a machine 

known as the BCM9 which uses a modification of the CCM principles and 

which has much greater security than the CGMo FurthermoreD the UoSo 

has under development improvements to the BCM whieh it is expected will 

increase the present sec~.rity considerablyo The UoSo Joint Chiefs of 

Staff are agreeable to disclosing to the United Kingdom the details and 

~ryptographio principles of the BCMD and to entering into diac.usaions 

~oncerning the use of the BCM or some modification thereof for possible 

future combined oomm.unicationao If the United Kingdom desires to enter 

into such discussions~ it would be convenient to the UoSo Joint Chiefs 

of Staff to begin these discussions in Washington in September 19490 

)Q In the event that a machine superior to the CCM is adopted for 

combined use 9 the UoSo Joint Chiefs of Staff must require definite 

assurance that the utmost care will be taken in the physical protection 

of such a maahine 9 and in accounting ror ito While it is t~ue that the 

security of traffic en~rypted with any acoeptable modern cipher machine 

should be unaffected by physical aompromise of the machine or its 

general prinoiples 9 it is considered fundamental that the greatest 

possible degree of physical security be maintainedo 

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

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