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U. S. ·and Br:i. ti sh Colla-Cora tion on 

Combined CJpher Machine Develo~ment ···--. . , ~. . "\, .. I 

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"The folloving memorandUJ:J. seto .out the Brit;sh and u. s. re- presentnt!v~s 1 underdt~nding or the result~ of the talks an~ con-· . f~rences wJ:iiqh have. ta.ken place between ~hem, on the subjec.t of · '·.cypher mELchine · development. for combined purposeEi. I • • • • • • 

. ; I ... Pre 11.mi~l-y' Nar?"a ti ve. · 

~ , ' . Duri~ the· cnlirse of-~he ~iscussions,, the British representa- ... -tive·s gave the U •. s .. represente.tives g~nero.l ·details o:r· their 

·,"double. wi:reC.. dr~s" which they· stated were being incorporated. in 

certain new ar1t1sh equipment, and deecri~ed in detail the cesicn 

of ·.a ne:w machine· re:r;erred to &s RM. ~6/32,, which they ·submi t·teC. 

i ti:iEJ'rt--fo:pm the· basis for ·a new comb1~ed cypher machine. The U. s. . 1:-epresentatives, o~ their part\~ gave. details of their proposals for .· ~~ _1m:?rov1ng the s.ecuziity of the exist~ng O.C.M. ·by altering the rotor 

:.::-.;/." . . iptepping. a?"raJlGpme:p.t, in addition 1to th~· provision of' "sets ~O.f 

-;r:~ · t,o~ats.ble .and interQha.ngeable cam ·?ontoilrs". The U. s. represents- ~~;\\ tives al~a state(i that they were aleveloping equipment-for. ·the !' ·, automatic wiring 01' ·rotqrs, and added that. they would make avail-

·.·;.:: able to .. t~e.British.de"ftails ofithis equipment when ft ,had-been~ · .... 

; .. ~·;~ ·. t~ied_:out.. _./: · ·" ~ '.; · . · .. "' . ·.. . , ·· 

· II. For reasons As stated in~ w~itten Joint u.~s. Memprandum,, . which was· handed :tq the British repr~~entatives, ·the u .. s. repre- !" 

J.: · ~ehtat1ves-"s~ted they could not agre~ to collaborate in tlie . · 1 .. 

. , development of 1

• tlle . R)i. -26/32 pl'inciple. for combined use. . The 

.;,:' .:· .. Briti.sh representatives, tor ·thei:r _part, stated that, whilst ag?'ee·- . ·: ·\ 1ng· that tl;le U. s. proposals £or the mod1f'icat1ori 01' the C.O.M. ~ gave considerably improved secl,ll'ity, they could not commit them-

\ · i :pelves to agreeing t~. these p_rqposals wi tho31t a very much m_?re ··· det.,1led study of them. . · . . .· . . .. v •• 

·1 •·· . 

· \ III. ~c~c .M: Interim Plan -. ~ · . ·It 1~ &Breed that tHe se~urity of the existing combined·cyphel' ~ch:l:ne·needs tttrengthening. It isrfurther· agreed that~ from the pl"ypt~Braph1c,-angle:.t the most aat1sf~ctory method of' C?bta:1n1ng. : ... · increased security,, Which is app~icable to all Marks of' C .• C.M,, .. is to altel' the code wheels so-that they are titted with rotatable 

i and "intEir.changeable· cam cbntours. · . • I• . 

•I ·• Iv·.· It is agl-eed that the U. s. Na'Vl' will carl'y out field. tests 

on ~he new.· type coae wheels fitted I with • rot~ta.ble. cam conto~s .. I ..... , 

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eclassifi ed and a roved for release b NSA on 09-20-2013 ursuantto E .0. 1352 DPY 

c~t·~·-: - <." - ~~~ 
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r~·> >:. . ·. -~ ;-;Jir lilM&-. --+- . vkoh t~1" have developed, ~ · th&·t if' ·:these f'~eld .teilta .are SuC- · ' · -, 

cbssf'ul,, they will submit,, tlil'ough the medium of the c.c.B.·,, a · -~-· ~: pla~ .for the modification~ ot existing and re·serve ·a .Cf.M. ··code : 

:- wheel~. · · · · · · ··· · · · -~ : .- :· 

· ·.1-~. c·~c .M •. Long Term Plan . : ' ... ·~ ... . . . ~~-:: .::;::.~-~~t. .... \.: .. ~~:_ift-: ---- - • I• '• -• 

- :·.. . .: •.. ' ·' ·- . ..,, . .'""'.-."•·~--·"':'.;;.· i;i"!ll: I , ' • ' • •. ·.1.-.,,:·~;-:.• ~·: .r ,,-: ... · ;:i•!-J.:::· ...... : •!!°..,'II":".• -d·:·~ !.,.-IQ, 

Having regard to th~ anticipated developments in crypte.nalytical i 

·liJachinery during the next ten to twenty tears; the. British are not ·. · · ·, . convinced that the existing combined cypher ms.chin~:; even ·wh:eri. ··· ··- ·- . ··--_.-·:; 

fitteq with rotatable and .. inter.changeable cam con~our·r:s ... as ~g~~-e~. · __ -·: ·: ~-. -~; 

up_o~ a.bove,,. will provide adequate cryptographic. security fo~. a liI&.fi .. " _! 

grade combined cypher machine,, and advocate most_strongly tbat . 1 

ac't:L-on should be. taken-Which will result in the co:rjl'bined cypher· · _- · ··· · ·--. ma.Qbine. to be used iri. the future. being sufficiently s'ecilre crypto-· .· ··· i 

graphically:- · · · · · :- ·, • • I • • I . '• ' , •' • ' ' ' 

- • • I I I • • • • • • .. • • • • • •• ~.. '::. • ,;::· 

· . ·,.·(al To allow re-encn}l.erment from one crypto channel to -: 

anothe.r to. ~e ac~epted without. re.se~vation~.· .. . --. , .. i . . : l I I

I... ... . .. T._ • -- • • • .._...._ --· ••••• ·- •• •••• ·-- ;.·. ·.~ ••• --~- •• ·..:.1.· •: •. ! • ; 

. ! i'_ (I?.) To allow _e~cypherment of the m~ssage as writt~n,, i.~. no bi.~ ctl9n_ procedure,, no burying,, no padding. . 

··. ~- . .,, .Cc) To. allow t.he P/L text to be ~?st~ibute_d _lfi~hou,t _para-···· · ·· ... j . iphrasi g. ·.; , . ~ . . ·. 'L ~ .. ,,,. 

· ~.. "(d) To avoid a~y .c~~e of c~de_ whe~~---~-lignment withi:q fi . ; .· . ·-: 

messag.l9; i.e. one message· set"ting...onl7 for a message. · · .. : . ' . \ -· ' . - .,... - . ··-----· --.. •'"""·jf ":11" 

; ~>l· (~°). For the .ma.~h~~e ~o ~b~ ·1~e f~o~·P/L: crib~.-- . - .. · ··. ! 

T. ~ .B;i ti sh. St~ff ·r~~uiremen:ts for .a ~~t~~ -c~~bined ~~ph~l\--:: ·; ·' .~· .. {.;~ ------

·mac~in~ ·are';, 1n fact; as follows:· •·-: t "'··· -·-··-· ._· .. ::: ~·--~~-. -· •• • ... ·.:: 

I.: - ·····.·;_,: ~, .... __ _ 

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(i) Mu~t provide top gra~e seclμ'~ty. tor.nex~ fifteen· • . to twenty years and therefore must be designed 'to : ·i 

wi t.h:~.tand the a~ti_ci}>a ted dev~l~pmen~s _ in crypt-: · ·. _.. . ! 

ana.lytical machinery during the next fifteen to . . . twenty yeEf~s • · · - · ·· - · ·- · :;:---:- · -··---·----,___ ___ _ . .. . :, ...... ·. ··-,::.. ..... . .

. ·· (ii). Must be aompleteiy immune to-'re-en~ypherment arid to----=··-. 

verba t1m cribs. · . . 

Sec"uritt .. 
~:-1·-·i" .,. ..... 

.:,·:~1-,1~;---:-··· .. ~~ I~,~~2~t~ ·ma ···--..., 

'-----

·1 ~1:: . .. ·.- · · U lllllUJ. ~L 11 -:- t... · . · : :.. U IWlf u 

· .. -~",:'!i ... : _ ... _:: .. \.~~}_.· :·· .· · ~~ _: ( 1 ~) ·. -~~:n:~~!~o-~:~~l c~:~i::d s!~!!i ~; ~;~~;er~: . . . .... ~ . . • .· placement of' the minimum number of variable ;~r.;;; ·{. ·< .. -:._;. . :;.· · · elemente... l . · 

· ..~> ··.; _-;.:i<: ·: ~:·:. : .· ... : ~· . ~ . .. ' \ .. _... .. . ~:~ ... ,:~ .,.·: .. '·:~.-.~ ... Fe.cili ties • . .

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• · . : :. •• t• . ~ . •,• ··~· " • . I • . • I . . 

• f .k ,) Io'' •f I:. ,( ~ •• "-"'· • ' o • c. I '' ,o 

-~~:~~<·;~i~.J~·-·:·;:a·:J. (·v) St~dard TeletYP.e "keyboard. 

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·~~·;;c.). ff:."-i< :~~,:::·-(vi~ Page print of P""/L te . .xt. and cl'ypt. - -i~;.--··~j!:i-:~ .i"~, t,~·(vii Crn>t to be in _5 lett~r. gr.cups. · 

~::i~-~~: .. i~-'t~'~ :~~·viii_ ·.Machine -to cut. a 5 '2:11!t tape_ in addition to (vi). -.~'.""~~ \.:-:."·:.:. :.r-.-· ,. ._...(ix . .Machine to accept anti Q.ecrn>t automa~ically f'ro:i:n ···~-' ·~·- -. '·'· I · .a 5 unit tape. . n · 

-~~!f:·)~r. .. :~ ·.;.:-.- · .: (x) . Nu:mber .of va;ttiable elements .requiring ~h.e.nge by . . -·~;· . .:7·,.~ ... ·:::. ·- . key list . to ·be r~ducec1 to minimum. --"~i.~f; .. _ .• l--~-~~: (xi) Message 1nd1ca.tor. proceduzie (initial code wheel . ::;i~-f~~~ :_-·:.·; .. :; .. ·.. . -: alipment) tq __ be as. simple a~ PC?Bsible. . 

r~~{:·:_:~~-~~-~~e :O-· s~1-~epre.sel'.ltS:tives, ~hit~I t admitting. that the .sec~i~y :.!~~'!;~·;~~qti;L_r~~D:t'5 ~s set out in V (a) to; (e) above .are a de~irable goal. ~ ~t-~· .. ~.~-~.&:im~a,t, are not completely _convinced .of the urgent need for im- . ·i::~~~·~o.v~ns. the s.ecurity of the cp .• C.M., bpyond the proposed .rotatable 

: ;.\•L'.~; ~P.-4. !p~.e~cQ&ngeable cam contC?urs an~ modified stepp;Lng arrangement •. 

··:!~-~~{~-:~.~-~h~'?' .~hey cons~der ~b£ t·: - . · . _; · , ·:-...•-.\ r· ·. . . ~ . }~;.:·~··: . ..i::;:;.P .. ii~·.(a) Prior to 'the ·development, production and .:f:ssue of any ·-~ t .-.:~AJD.P.~ov~.a .combinEtd c'jpher machine, an assurance would . have tQ be · "~;.~~/·""Qbt~!ld. trom competent Britis~· authorities that uniform U. s. and ~i.'.#;:i~.:·ar::(t~-~ · .rules wo~ld be observe~ regarqin.g the_ sareguardi~, dis~ : .... :.,.,.~. tribut on and use of the new equipment. . ~:;·;·.:~ .. ~'::.,:;· ;.".'". • . ."v·. . • . .. ,:·. ; t ... "I . ' • • . 

--!.\~· ... ~'t,:~, ··. (b) · The question of the use of an ·+mproved macliine VE[try ~.-~=!f;.:'~,~~a,-gel7 hinges upon the acc·eptance, by the British or .~he proposed .::o~t·"'·.tt. s. llqd.1ficat1ons 'to. the c.c.M., and consequently J;l.O .commitment ... ~.: ·. :_ ... c~n · bttt~ .. ~de at th1_s t:f:me that ~n 1,mproved machine will def'ini.tely -~:;: ~;. ... be _ajiop:ted. · · . . . . . ·. 

:~~·r~4l.t·· ~l is ~-gr~e~, therefore, iha~1 the·· toll~wing -~cti.~n sh~ul<i te 

•ff' ___ :_~attr81dered: . · '· · ..... _ 

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:~~i · -~ · · (a) . To dl'aw up a set of,.~greed rules f'or the safeguarding 

------ ~. -.amd ~~tent and m~tp~~ o~ diatri~u~io~-o~ the improved eq~ipment. 

~ .: .. . r·· .... · (b) Th,e ac~~p~ance, I b;r the :Sritish~ of the u. s~, "propos.ed 

~... 1 ··modifications to t~e~:~.C •. M •. ; . . · . . . . 

~~~>. J ··, .. ·.,° -. (c) .. Toi dl:'aw, -qp a~ ag;e~d s

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et. of' enc°yphering rul~s applic-

. _.. · .l_llbl~. ~o. _the_ new. ma.chin~,. acceptabl,_ to both the U. ~· and ~h.e :, 

t-i·. :.-1-.··-'.B"ri ti sh. · \ .. · · ... · ' . . , . 

<\.fP~~~::•· .... _ -. . . . ! • . • •. : • • . : . . • ' • 

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· -_,,.:m.n SE&R\fl COPY 

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:It is agreed that in addition to (b)·above, the British auth~rit1es will consider the.exi~~ing-U. s. regulations v~th a 

view.to subm1tt1nc a draft se~ of· rules to cover (a) above, and 

that.' the u. s. authorities will consider· the British secur1t7 re- qu1~ements already set out 1n paragraph .v (a) to. (e) as a basis . . . ..=.:: 

ror (c) aboye. . :. ·. , : · · .. · .. -~·=::; .-?;°-;"7."":-·-~ · ..... ·-_.---~·-·=- ----:-:---··.,·~-::fir!= ·' . .. ... .. . . . •. . . . . . . . :. .---· . .:.' .· VIII~ It is further ag;-eed, that: .. · .. . ·.-.· ·~- ._ .. _ .· "·· .. . --· ' I • I • • I • •, 0 ; 

(a) In spite of the adverse··u •. S. co~ents,· the Britisb· . : 

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.will continue with the· engineering development of the BM.26/52 

principle, and w.il1 make.the result of .such research ava1l:able ·. ~­

to the U.· s. authori~ies, _if, in the.British new, it is likel7 

to have any comb;Lned app_~-~c~_ti:o~r . . ._ i .. ~_:m .. a-.. ;:=aa • -:.r.: .•. ..ii.~;;ii·--Bs;;;;z;;;;;;;;;;;&;;ii;i;;;;;;;;;;;. ;;.: ·$1~-:~SFl!i: __ ...... , · ··.(b) The u. s~ authorities vi11 .continue engineering 

rea·eatoch on the ·u. s. propos~d c.c.M. modifications, and will make . the ·J:tesul t of such research ~nd development available ~ the ......... , . ... ____ ; 

·Erit1sh ati.thorit!·es. · · , .. -~·.,.. - .. :..:.....:...:...:-:!:-.:-=-.. · •·; -·=.:r~.-.-t:.rcl~'. . I I ••• • .. : • _. • ·- -~_:;: .. • ~::!·-~:....-~~-:-;:::·- ... -"':9::=-··". ·-:-w-':··~-~.' 1

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:;[X. ·_tolla'bol'ation on the Development ot C~mbined Ma.chine f'OI' ·· .. __ .. ···-··-· . · · tJse bl Lower Echelon. . , · . ___ .. ,..,_;~~- !lfF-! . .""!'•.,.rm:sz".;"·a:a?'·.· .• i.!t.•k···· .- ·.·~ • ·: • . • ·, .. I ·. .f'"" • • •':,._ . .:.:......--:.--. ·--- • ·. --=· ·;-:-=:-:·.:.:-·:· ·-=-:1 

' . -~lthough. ·no .J!.gre~ment was reached,, the British representatives ur3ed.: tlta. t the U. s.. repr~sen-ta ti ves should seek. and obtain· the ,.. necespary· app:tao:val from Higher Authority to collaborate with the . -]i'. 

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'5h in. th~ development o~ a Lower ~chel~n __ c_q__~b;n.e.d ... cyp~e.r. , . _ ··!-· .:•.

m&C :b.e . . ' . . . , . dt i • - . . ..... : . • .... ~"J -----·= .l- ..... 14 ="'-~: 

• t • ' • • • :u • ·-- • • • ; ~ ." ~ •. •" :· .. ·: •: • -~= • • • •:. • • -~..Jt?.~-.~\.-~;?-r:i I 

X. Conclusion ·· .. ~· · l. .. . . · · .. ·_1.·~1'~S:·U i._: -. . ':"" . ~ ' ··- . - ·-···. . - ··~; 

. It 1s. mutually ag~eed .. tbat the series of' .talks· and conte;-ences , .:~;: 

bas be.en oC great a·ssista.nce ·to both. parties, and it is r.ecommended d:.1 that collaboration in this· field 'should continue within the f'rame- ~·-:-;;;;,_! ---

work of tl'!e agreements a.et. o_ut .i:D; preceding"paragr_aP.~s.'!. ;·. ___ .;.._ . -···-. ·i . . . ..; ·.: .... ·-· ~--~~··r~-· -.- . . , J. ' .... 

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