:frms 

Toi 

Viat 

Subject: 

REF -I!f: A243592 9-

g ,o :p I 

Jl .. t A&n1ra1 Nimita ~-02, Or-OJ, Oi-09 

1.3 ltarch 1947 

Cellabora.tion !>otwaen Uritiah &nd tl.S. on >evelopaent of a aew Combined Cipher ~hiM 

l. During recent discussion between u.;. and B?-itlsh ropreaentat1Tes, tho .3ritiab proposed collaboration on the developaent of ~hat they te!'Jfied a new and revolutionary idea tor a 

eipbe.r 11.Achlne. Thi• Yi&ualiaed a 24-~}ieel ll!ach1n$. Our opinion 

•• that er7ftogra.phically t-ho rropo11ed Bdti8h ma.chine Ttas 

good, but it 'fiould b9 highl;y coiapl.icated, a.nC not practietl for 

eua;inaerincl and 11!\B.intenance reasons. 

2. Our cou.nterprc~~Hs&l ns t·•• introduct.hm of aodificaticrns to the •~ieting Comoilled Civher :.:a.china which would gre~tly 

•trengt!.en it or;pto~aphic.s.ll7. The .British will consider our 

Pl"'>POSal, makini a det~iled study thereof. 

J. le proposed !'.ll'ther tru..t lhere ahould be better Security Rules to properly aa!'e.JWlrd 8IJ¥ coobined oryt:·to system. •"e 

feel tha.t •hile the .British are securit7-mineed, they should 

provids better pb.J'sical securit;r for Ol7Ptu fiia.Chi4a. 

4.. The Britbh crntD personnel have returned to the United 

lingdQI!. The1 will make a. d•tailed study ot ou:r prepogals e.nd 

tol'llNlate a now eet or sec;neity raiUJ.atione for 8"4'bmlsaion to 

the CCB.. We will t.hrouiihl.7 test our proposed moditlc.'-tior.e to 

the pretent c1Dbined cipher aaah1ne, and mtlka tM results k;:..010n 

to the Britiah.. ne 'trill a.lao eublllt a. new set of aecurity 

n,;.-ulations to the CC.B fOl" eonaidera.tion_. in order tc attain a 

autualq :iatiafa.cto1•y security baala !or fU\Y tuture col.A.aborat.1on. 

5.. The Sritish indicated that they know a great deal about 

the tX;:l as a re~u..l.t or observations J.uring the 'f!ar. Act'..tall1, 

th• !ritish ~ere n•ve~ given the zc~ otricialJ.¥, ~~thou{h it 

•• uaed in ce~in Bri thh C~tuld• with U., s. personnel provided 

. Declassified and approved for release by NSA on 09-20-2013 pursuantto E .0. 1352\J , t 1 c 
REF ID:A2435929 

to operti.to a.Ad aat~ it. They have th~ h1~hest opinion of 

it !'rola a crr,pto security v iewpoir.t !l.nd proposed tt~t it { ;c:.t} 

be uaed ~& t::c high-letre1 combined cryptD aystai:., lneteiMi of 

tr,yina to develop a. new combined machine. ~e do not fa.vo:r t..hia, 

the principal reaaona 091.n, .. 

a. We would lo .. control of it• physioal security - which •e have thus far ••na:red to lmintain ei"fftetivel,y. 

b. It the ~ ahould got into t~e hands of any other 

nat1on,, it ;;igbt 1Zl the .future !:>e UHd for traffic which we 

prwbs.bJ.¥ cou.ld ngt read, 1.f we so de$1red - at l~at not Tlthout a frr!f!!.endoU! expenditure of fw::i.is for anal.,rtlea.l lllaChinery 

whloh doea not ;et exist and for employm11nt of lIUJlle.rous par-

•onnel to operate th&t.JB4Chin&rT• 

e. ?!e feel th&.t the cVJ.11bined cipher mae~ine {Ceft;) we 

rro'i' have is eeoure .tor o.vmhined use, and with prti'j?o&ed l:'lodifi· 

cations should be secure £or ~ years hence. 

ct.. We b&ve no better cr7i'io device for our use than 

th• ECLJ anl i.t 1ff.I shll1"ed it with &ny other nation we ~~uld have 

41tficult.r app)¥1ng modifications to the ~>!. in the futuro. 

Thia la•t ite; 1• erlrGliivb,r ltapo~ecause our only present 

~r.~u.t:Or ~to ncurity-Ue in ~he filPruve<::ent of the 

---

6. I! the pr•atnt co~~ined aipher ~achine shouJ.Q be co~-

pr~iaod, and 11' t.ll$ Brit.ieh ~lid u. s. are allied in a future 

ftl', we could give the 3r1tisb the F:CM (if that ahou..l.ci then be 

neeesa'ir"J). aQ~ever, at this ti•e, I reco~~end that our present 

polic7 oJ: reserving the iieii strictly ror U> S. mill~ry ~• be 

continued and any rel.9.ntivn or this policy b$ resorted to at 

a. later da.t• only as a.a. -ext.r~e lilllereeney measure. 

7• If' wa collaborate nth ths British in the future on a 

uew ao::;uiaed cipher machine) the Sri tlsh will p.,..obably expect 

the u. s. to aasume major reapon~ibility for engineering dev9lopaent \':Ork.. l d~ not believe th"'t the British will reprodu.ce 

our ?t;M for theil' own use - even though the7 cl.au to know the 

basic principleu vf the ~ bec~use of ~xpense and diff lcultie~ 

involved. However, this la a poHibilit;t, which ~ ahould 11ot 

eneour!i _;e. 

8.- '!his reoeut combined ery-.,to ooilfer~wce 'D!!I o£ value to 

bcrt.h iiritbb. and. ti. s. l rooo1111aend that we (.\rm.; anti i~s.vy) 

contitt...ia present liaited eryi~to c01.l.aboration ~1th the Britbh.