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'?O: Chier or 1'•'ftt.l Commmic&t1ona 

ROOll 272)1. Department ot·tha lfa'fy W&ahington. D. c. 

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, · :1. netez-eno• 1• •4• to -th.e atat ... nt, dated 29 October 

19\7, but onl,- recentl.7 received rrom the Sel"tv1oes Cy:phel' Policy Co-1.ttee ot the LBID CJ"pher .Po11ey :8o&rd~ subject: Mod1.f1ca.t1on8 to Improve th.e Seourit;, or thrs Com.b1ned Cyphel' Kachin• (lncloaure l). 

2.· In connect~on v1th P&l'&£l>&ph 12 or that docuaent, 

in vbicb the s~p;e!ltion: is that th• u. s. a,ea.tn re-exaaine 

th• Question, the Anq 5eeurit:r Agency pro:poae:s that an earl;r · -•ting be held. between Army and Ravy re_presenta.tive•, with 

& vtev to dec1d1ng,and agreeing upon a joint co~ae ot 

action 1n the .matter. -

·3. It the roregoing p~oposal is agreeable to you, ·1t 

1• aus.geated ttat the •••ting be· held &t A~lington Hall 

Station on a date vh!ch !z mutually sntiar&ctory and vhich 

can pe &rl'&nged b1 telephone. 

l Incl 

Doouaent ot Servieea 

Cypher Pol1ey Committee 

HA.?tOLD O. HAYES 

Colonel, Signal Corps Chier, Army Security Agenoy 

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Declassified and approved for release by NSA on 06-06-2014 pursuantto E.O. 1352a 

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l.iQ.DIFfdATIONS. TO DiM?.OVE THE 

SECURITY OF TJ:IB COUBINED CYPHillR MACHINE • 

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1. It is '!J!:)W generally agr0od that there is ~ nood for improving the · · security of the existing Combined Cypher Machine ( C. C .~,iI. ) • The British 

authorities cannot contemplate any modification which would fall ou·tside · · 

the scope of th~ Typcx with c.c.M. Adaptor; o.nd it is thought that 

equally the ·u.s. au·chorities will certainly not consider~ aey modification 

which would be impracticable on th0ir EClvI Ad,nptor or· on the o.n.:M. Mark II. 

. . - 2. ·It-is considered ·ch..'l.t tho possible mqdifioa.tions ce..n be divid€1d into 

· tvro general ca. tegories : · 

(a) Modification of tho stepping soquenca.· 

(b) Introduction of u. ptugbpard. 

3, With r<.::gard to (a), two p:i:oposc.1~ have been put forirard by the u.s. 

authori·ties. These ore :'."" _--;'""-"-~- ---......,.--

(i) The introduction cif rota.teablo and interch.o.ngoable 

orun oontours • 

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(ii) A oomplotc ro-.nrrD,ngomcn:b of' th1;: lo.w of 

progr-0ssion according to which the drums advance. 

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The mod.ifico:hio~ required. by ( i) iu thci.t t;h0 uxisting turnover notchos 

cut in ·t;hc fix~d rim of tho drum ore machined off und rcplnc0d by a thin 

metn.l ring. This :ring1 which. 0<-'U'rios thiJ turno_vt:lr notches,,. con be 

fitted to tho drum in 3.IlJr ono of' the 26 nngular positions, nnd o:ny one 

of o. sot of such rings cn.n bo fitt0n. to o.ey drLUn. 

11-e This modificn.tion is oapn:blo of being applied to ... botli 'the U.S. nnd. 

Br'itish versions of the o.C~U. It is undGrstood that fiuld. trials o:ro 

shortly to be carried 'out by the u.s. in·bo the reliability 'l'tnd. 

p~rform~ncc of such a device. 

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5. The proposi'.11 would unquestionably give consic'l.orabfy higher socurity 

to the o.c.1.1. 1 but i-G would not eliminnto tho short cycle of the threo 

centr0 drums which is the fwrlruncnto.l wcnk:ness of the machine:. The 

security would. still be below thnt of the Br'itish '.l.1yp0x Mk. 22, mid nlso, 

;i.t ia belioved.1 of the u.s. intrn high-gi:-£\dt:: mo.chino cypher. 

-6. Tho schG.me. mon-cion~d-· ~.'n. pnl:on •. .3, (ii); ·is as }~i°io~is : '· _ -~· • ' I , ,- ' \ - •·• ~::·~ 1_ cNumbcring tho drums from °lc:f't to right, d£liri--3 moves with l:)Cl.ch 

encypherincnt as hitherto. Drun 3 oon:brols drum 4 ClJld drums 3 I 

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. ~ ::.r - ... ·{ .... ~ .. .;~,;-. , -:~ b,. _cpil!~B.~ control .~lJril~ 1 ~~ J!-,-. c;ic_lamot:ric: ~R!'~p.ci:Pi'i" . 

~:S:_-!f .'.Ol~-}-t.c:o.~W:-~"[~<!J. .. ~~T_ d,J'.'~ -~9ntr:ols ~~-· _' - : . . ,. -·: ·· . .;.·J~- ~ •.•::.·;;.~'·•·;· ·..;,;;.•-.: ;·.~ ,-:.~.~,;,;;j-;;::.___ ... ,_~~ Z/ · • · . · · .:!,'F_.;.. . ,1 . • . --. ·, I 

.. 11ai~r~~ l;i-f ~~~(~It-~~~~f~~~t:~-:~~~1~ !~~i1J t~ ~~~~f ~1~~1:~ ~f-' ~~rov:m~~-e .. ~ .no ~2,~cr __ tl!!~o~ 1!1~~~~1.-~at~oii.-wou).d ~.,_ye "this. ~f;fcc'\i. - - ~ - It ~'l.o tno _i'urtliGr (idvroij;:igc of' l"C:moving the I).coes·ai ty f'or any -

. -·z.dttt:fction tti: ~~~~~}~;i?~f~~~-~£;-~~~c~Iir; ~r t~e- tur~;r~_}iotch~s ·~- . q:' 

1 :· \)~ -the E.a·.~~·:.:1~1;{~: ~wer:&~ii .~l{~rr, ·-the .act'iv:i-t~~~r- tho ~- ·i • -~~--::- ·• • • 

.. , ~ufnc;)y0r jp.vris whicf-i:" udvanca'·"{;°fu3'-arums--Is-~controllcd by s~I~inoids whicl1- -

. axi9 tli.Gnis.clvi;:;s''ooP.trpT.lc:d ljy'"r"OiO:ys. 1.rh0so rolc.ys urc -opcrn.-Ecd"b:Y:- 'smnil -_- . --~ 

.. '. ·lovoi·s Ythich• 11 f6llo~1 "r.thc co:ritours· of'-tFw rim in· 1<7h'ich -thc"-l:;urnovei;;· - -~,., - . ·-: - -- ; ·• : .,._•. . . ') :; ·.· - ~ .... : .. ; ~ -_; .. -. "= ·W ..,..'-"'""'_ .... _ :· r~~,·,i:_..,.=- ··- • ··· -·- "'"- •• -.-. .-.:.~.~;":.:!~.I ·t~"""!'" .. -~ __..-y ' _.,,. :.- -···!!"~ .. '!·':L'"'-=I 

no:=f;ch\:ls arc. cut. j3y rewiring tho connections botwoun tho rola.ys n.nd tho I 

· ~~{~~~-!ario~h~11~~.£!~~~i:!~4~Ia.:.6~~;u~tu~~r-~~~~·.~ fi£i~~lii~ ·-m~ch~~~l':~ · -- ~ · ~--i the turnovGr J?._"..1.Vls- ore con:trollud by a p..tr6ly mcch.:tnioo..l device WhicfJ. :is. -- -- - i 

onJi;ircly 3'fl. t:isfac:tory .. in-fil10 C~f.:lC whort. on;j"CJrtiriJ. . c·ontrols- i·bs -nol:ghb'ol:i:r • -- - ··- .. _ .. 

·:su.~ the. modificn.t:i,._on. r~.qutr<?i ·-~hit, am~~t 0t1i . .1:1-.; • tnI!fu~~,. ari.u-ii .. 1:-·shoula· i 

control d.rwn 5 .::~rrl this 'iould be -exccc.diugfy d.1fr:Lcul t t6 . ei'foc~ with -- tho existin~ mcclia.lii&.TJ1 •. It is un:lcrstooa· tci bo .fh0 "opinion of- -the tr .s·. 

cl\iineprs 'th:l.t this mo'a.ifl.ca·don.'would be pr~i.cticiri.11.Y. iin]?o'ssiblo on the . o:o.1.1 • .Aa.~ptor.. · - · . · .. ~ .. '· · -

a~. Ir thy. ~~ifd~~ttorJ~r1- (i) -~ :3- :(ii.)''~~~tF~~J;~~c:·~~~L~-·~;;:~ ,··· 

thq sec~ity' of the miiehinc-- vio'uld be' very grci5:Elyl.ncrCia.ocd, out might. 

·;. still ·'tic ·r:ithor iow(:.;r"tha.n the u.s. iritra hlgq_;efac'lc ma.cliino ri.nd the -· 

:British_ TyPcx Kr\r_k: 22; ·- · ~"' ._ · ... ·~-... -.- ·-··--·- · .. • ·· '·' · - · -,·=•· -

~ 9 •.. It soc;s to us'-.~tkt, v{i irin ·t~~~ tf~c~~~~f~~t~iii· ~~1:n~.t,io~~. k~-~~ by thu two t;-7pos o':F c.c.!.f . .M.aptors, the proposii_ls )-(?--) 6.nd. 3 (ii) .. 

exhaust o.11 the re0-i:sori:iolo pos6ibili'bit:~ for impro'rlng ·the stdpping .... arra~ngumen:bs of the mchiri.<.;. The· only other .Jxpod.ion·i:; which. -i,.crnn.ins 'is . i:;hp intrCJductil;n of' a. plU8~bl:'.Crd _on the output (cypher) fJidc of the 

mnbhinq. In thuory, •,Shis i::: no cloub-b :Pcrf~ctly 'pom:iiblc ·on both thc:i U .s. 

nnd. the British version· of' tho m~:i..chine,;· .it. ·is-thouGht thnt the U .s. 

·authorities woulu ·00 ·vory rcluctr.'..nt to ugroc to its- inJi;rodt.totfon • • ,. •• , ... , •• I •• - - • - ' • -~ ~ ... ~ .' • ,; :- I • ~ ... ·• "'· 

J,O. The ndcli tion:'..i- scc\.iri•i;y which c. plugboard. :vrou1Ll -ai'fqrd is not over- . 

v1h,c lm~ngly lnr go• Tl~~. i~o0;~ori for th}:3 is· ~h~{ H1c fm7::u11~n~r-.l ~hort c~cle 

of. tho throe con·brc drums is no·I; th~roby dE.:m;royed. 1..oclificn.t::wn 3 (:i.) 

nbqYO coupled With thq i~truducti0~ vf i;t pll;l;IJbonrc1 w6u10_ 3tilJ.: l.;:;a,vc t~C 

m6..C..."1.in<.: less SC::Cll.I'o..l, ·hli..:-n both Typox i.ik. 22 c~nd the u. s .. intra. hlgh-grnclo 

nib.chine::. . .;:. i -~ 

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We a.:..·o 100. to tho fc.liowing c1)nclm::imis-:-. 

(n) 

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.rhl:l only mctlifiba:biob we c~n cnvim.tt~c which is cia.po.ble 

uf rc.iE~i~ tho ~,·ocurity of c.d.J.:. ·to the ll:lvcl of TYJ."lGX 

Mk. 22 would bu n. compic·bo rc-ru..,ro.ngc:ilnerit of the· ln.w uf 

pi·ogi.,os-?icn ·.:;~'·the m::-..chine. - ,· 

It il3 l:lxtrum.:.ily doubtful if thi~ rmuld b·c. a pi... '.",c·bim\l 

I>l'..opoatic.n __ for tho :ikiti:m C.0.1.i. Ad.apter. . ···•- £ I: ~ - ,;. . : . 

Tho addition...._l p-ec.i.1.:ri ty afforded by C'.. plugbμnrd. would 

sco.r'ccly ju::rtH'y tho ti,ouble ~1 (;Xpdnse which woμld .. 

be cmt:i .. ilocl. · 

'fhll. bos·b prncticc..l · st..:.p is •i;o .'.'.:ccoi0I'c.t0 bhe i11~.roduction of rotr-.tcb..blu n.nl int·:irch.."l.ngGo.blc c:un corrt;ours. ... . \ - . ..,, . 

( c) Evr.:;ry c:frort should !)C tn..'"1.dC to rcrwh ['.gr.:.. .... mcmt wit;, ·t;hc;: 

U.S. au'i;hori t ios in tlih0 dcic:.igu a.rid production of c. hrn.nrl 

new cyphur I~~chinc fur cnubincd P1-1;'_POGC::B. · 

12. With rcfur~n~ to pa.J?:tr.;raph VII (b) of ~ho. ::t:~.::utl U.S. -:si:-itish 

Marnor:\rulmn 11U,S. mld. Bl.•itinh Oolla.bura.'i;ion oil Ocanbincd. Cyplwr 1'1,1.."l.Chin1J 

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' ' ... ., . .. . .J_·. _. Dovclopnunt", do:liod 4th ~i'U'ch, 1947, J.li is sugg~f..:tod t"fut the U~S. 

; 1-.:u. thori tic.s might n.gain rc-ox['lilinc the g_u·~ntion in =the light of j;he 

n.bov.e rumii.rkp. Wu fully ~.ai t th.at tho only iclons which we can 

rc.:::n.oorfribly p.it furv;a.rd for ·~he improv·.:.mont cf tho ·s<:;curity are ·f:till 

imdcquo. to but should be gl~ "i~o knrni whether tho U.S. nuthori t io3 

co.n.b~tt?~ th0m. It mu!3_t a.g.iin bo strcos~d.hov;0vor, thc.t ~ mo._jpr 

modific.9.:cicn .of thi:..: C. C .~·~. er tho p:i;'uducticn of n. now ma.chine o!:>.scd on 

old principles could not 'b.J ·contompl::?.tcd by th0 BritfSh. : · 

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Office::: of thC?._ _ _9yphe:.:r Policy' Bo::.i.id, 

··· 10, Chos·t...,rficlrl Str0ct;, W .1. _... _____________________ _ ' • 

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