(a). Tha Brit.ieh version ot the c.c.H. consists ot \he Typex 

*Sf'tht"ne wDh \he c.c.?C. ~tar. 

(b). Tbl'.! 'l)pex machine ls ane ot the Brlt.lsh natitmal cypher 

qllti·-n ii1d h ~ec:l to be replaced within \he next n.w,........ . (o). The c.e.a. adaptor la at no value wtthant the Typex -.china. 

(4). !he a. Hzi.Uah G1Jl}ler macbhe i11Mt. incarparat.e the mechanism 

I/It tile .-a wr Calllb!Ded cypher l!IN:htne th ar\'ler to Net \he ~E 'DB\ fll: '\lie &oJal. lfaYJ" tba• tJie IA'iiller ahlpe aball •· 1, dd7 one lllS.Cld'.bll. 

(•). The new Br1tiah cypher machine Jll1St be etrect!:na fr:tr the next 

Wed) 1ti81"8· 

(t). n:e a.sign ot the nn Britiah CJPber nachine is at present held 

11p ,PiJJl1i'C a dec1a1an Oil what lieebantm 1a to be emplqyed f~ 

~on rostcat10b8 Gt a lang 1iei"m bu1a. 

•• 1 6. ·-·-···:: .... ZSiFii',._t'rGfii!?- ..... ,-- --·-·· •-r-···$-'i Bi. F. Sj-·,w·- -- g,-·- ·--··z-i!JF.WC"'. 

:J. the S...C.il,. fa a t!ve drus machine. The druTl turn•over :aechs.nisn ~ a mtertal bqiro•ment over t...i.e c.c.•. hth the B.c.M. am the Typex ilill!lOhtnea oould be Dl0d1f1ed to aceept the 5-dram r..c.a. mec'.h4.l1.1.iftll. 

· ,,.~ .... -- P1 ·1 z·1r ::· r rm w--.·-· .... - · ·a · · -q· er·. - l - f. ·. i. 

-'· 

(a) a set d! the t.e!l rotors "i;-;::;-. . -

eclassified and approved for release by NSA """1f-t,t-t!-::,__~t""ti-.t-ff-......,.~~~ n 09-20-2013 ursuant to E.O. 13526 ,i _J S.i'.-.:n·;.~~~~.ia.a· .i:~~.ia ... -~·;.~{·.~:-.;,;~~;.:..:t~~'..,.:~~~_.-·~-;:.,.-=-i.W].--: ·'.,;._~--~~~_:::· •.. -:-~R 1!::9.;•" • • .. • .•·-~·.:...-.. 0 •: .... ;_,i... 

.., 

~-. 

·;;·· ··-

. 

, 

.. 

"!: 
-

-+lf-ff-~~i..n-;*""~~.-..;;w.;~B 

1.llJ l..'UU \.L ~ 

(b) a 25-letter"crib1 

0ntt Reh a •ch.ine oould thearetic&u.7 eol.w a setting at • 5-drum cypher .... 1'1\h a ten dr1a aet ct: rotans in abao,t two yean. 

6. The prac\icabil!v ot such an attaek would depem ons-

(a) the mmber ot aa.ch1n.cs which could be made avallabl•, . . .. 

('b) The a:tent to which the speed or cperriion of such a machine 

.e1*dd be tncr.-<t. 

1. B ia eatinated that 'the f'1rat aaelrl.n9 ot th:la type-would ca11t abou.t · tS00.-000 and that flrrther •chinea would cost &ibout tl..00,.000 each. It 1IJ 

.atlo1pa1*d that cQmJ1denbl e improvement in the speed ot uperation at a 

~- ot tlda ~ 1fOUl..d be possible Within. the. next !'1ve years. 

•· !be 5-drD s.c.u. tJ,:iough ottering a 'mawiel iaprovement Gil c.c.r.t. 

"111 ~dare theoreticall.7 not def eat tbie tarn ~ cnpwnelytle at~ in ..... TMl'• ti.. .. 

9. !he al>O'ff appree!i&\lcm applies w all 5-drum Q)'Pher mns and not 

t!IZelulvely to B.c.11. beT&r,. a '1-drtml cypher •• 1rtJDl.d defeat thie fot"B 

v1t. utack. · · · · · 

. . . 

lriil•h eonclusloa. on :mitabllit7 of B.C.JI. _f'cr Ccxmined C-ttmmnications • 

. . . 'i · , • i i 1;;;; iii iil;:U$i. . . . ' · . · .. 10. Di Y.tew or the tareg1:>1Jtg tht!! Bri tieh could not cant~>late building 

• ~B.C.11. 

μ." .l 7-drurl ~~c.M. would be acceptable f'r(Wll ti. atand.point of ae~iV 

wt ti'Ob1.d 11lwl:nt the inc~o:rat!on 1n the MW Brltieh eypher zachine at 

tr.clattionel mecbaniam,. 

;It A. Par\ k't 19} JlW.&h 

12. llrJie to ¥CCt Uaita\1ma in the I-;..Clltitt,. the u.s_ aennot at preeen\ ~oaate a 7-d.nua n .. c.a .• wl\hin the ca:rCaSe ot the t .. c.ZJ. They can~ 

MOt:•oC!e:te a ~-an. B.C .11. whan11111. Qi the o\her hand6 thr~ u.s. haw 

alreir47 buUt •. 1~ meohenl• tar usocla\1on wlt.h \he fn>ex fll!lChine. A 

'Y-ctrm. B.C.M.. ~la theretare lmlikel.7 jo ~ ava1lebie tor Cembilwd 

Cr •idcattons tr:1r .several 7e:ara. ·. · . . . , 

lJ. It. woul.4 tUe ab«lt two years be.f'ar.e the ;-drum :e.c.M. acle,ptell" could 

lie dlllable. 'l1ds being ao "1th t.he arrl ftl ot \be .new Britieh cypher machine, 

the ~adaptor wCuld be obsolete within three 7fflr11 ot ita introduOt!on. . . - .. . . 

l.4• The DriU.ah would therefore be •xtremel.7 reluctant \o build 5""'1!Ua ir.c.•. adaptors as a BhGrt tel'm solution. · 
I ; f ·1:; i I;\ 1 !J t_i· : __ ·~ : .L 

17. Yo proyide a 7-cb:ta Cmbined qa"tat 1IOUl.d ~ llOdif!caUua to 

the u.s. i.;.c.H. bu'S need ziA requiita all1' ~ llOd.U'ioa1;ian to the new 

Di-1,lah co»ler maoMna- 1f !;,.c.w. pl'inc1ples are el!l(llo,red. 

is. Iii shcd.d be pointed °"" tha\ 11'1 -dew or the . •terial. arl'VMC8 1n 

c:eyptagraphia tecim!qaa, the Bri~iali 1l'Cll11d prerer not to eapJ.cv either the 

n.c.t1. c:r the ;~.c.a. pd.no!pl• in \be new Br!.Uah ~ lllllehJ.m. Hmewrt 

un'ldl. dJ.eouas!on between Brlt!ah and u.s. an all 017J>tcgr&ph1o prlnoiplM 

and tbeori.es is authori1led with a dew to an1vi!Jg a't an agreed ~ approaob 

to ti. ~ the llriUah a:re tca-aed to Nta1n a tftl:fmd.as ot th1a cie8ca'Jpt1c:m if C~illed ~ 1s 'Cia be poes1b1.e and 1t they' are to inoc:.rpcrate nBriuah 

Nat1cntl a aa ~.ll 1us ftCCllbinftd" principles within mm maohine, which 1a & :requL ~ of the :;,~ iirf7• 'l'hia requireMn't ill not so ~ed in t.~ 

Aft\Y' and Mr F~~ who at present 3ne teehrd.qUM ~erent i'1-a3 s .. c.a. mi 

?: .c .n. in t.1111:t f1Z Ul'lder co:wtl'uctial, ~t.r bo".Ji "m-J.im" cndnatt•litw" eyp}• 

warik.1.ng. 

19. D:t vi• at i;he nnterial achamea noent'l:- mrill in the acienae or Cl7P~ and ~by, the JIOe't effect!ve eal.uttm to thf.a }rd>lem 

wauld bi! achiewM.i bJ' n.. ~ berneen the Briti8h and u.s. <'IE all ~h!c techniques azvt +.Mcriee11 wi.thGl&ii nee~ d!aalcwing whl.ch 

at tbeee were to be ~OJW!d tar naUonal ~channels ot either natim. 

This would P.mble the llDIA protitable CWl'81t Sn wnw ot seouri:tq, fdf'1e1ency 

s:nr1 pncti<"'.ablliV to be ~. Fa!' irJ« th:ttt, both mt1ona are td.81 

'\o the r.c.w.ftj.r.M. ~es r,,,. Caabimd CO!dD'liafltiena rrr thfJ l'lf:Xfi 

twentiJ' lf.':U'S• 

20. If th1e exc1--- at 1Dtcrr.aUm 1a ~ ~- +.bftn 1n view 

or. the tan ~ ., de&dgn ot the new Jlr1\iab (.)'phmP -~ .ta hftld up 

pelMMng a deoiaim .an what sptea ahall. ~ euplc.ved tfll:' Cmbined uae m a lOE& 

~ baaia1 a deo1a1an m8't be 1iaDn withcut delq on whethmn• 

(a) the 7-dr'ula 1 .. ;.c.w. 

{b) the 7-drta B.C.JL 

(o) botlr•) ml {b) abo'8 

am to be ~~ f~ tbs.a J'Ul'POlll8• 

--- -· -· -· - - - - -