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. MEMORAr~DUM FOR: 

:·via\: 

~F ID:A2435743 

Op-20 . 

Op-20-1 • 

I 

. :. 1. In order· to provide a high grade• high speed, 

and, :}.'eliable. mach,ine system for encrypted combined cornmuriications, 

'_ap.aptors were built to modify the British Type "X" rn.achine and the 

;mcu. The adaptor produces a new, third machine system. The advan- -. ._tage~s and disadvantages of issuing the EC:M to ·the British, versus 

. ' .. the adapt.or, are lis:ted below: 

Advantages !QM 

· . .- _ . . Cryptographically superior · .,,.. -~>-.,:~~:to adaptor or Type "X" 

·: . · · ·. ·;, Me.chanically and electrically · .superior to Type 0 X0 

· Di_st'ribut:f.on can be st~rted to 

British!a:t a ·rate of loo units 

'· ., :inonthly commencing l iDecembef, i. ·:·1942. ' 

'.' . :~;_ .. [ Primary I combined naval communica-

:. _/;fj. . ti9n problem solved by early · .r/;~~-:... ___ Spring, 1943• _ . ·.: .. ~.;;. Provides U .s. Navy with finest ....... __ · · >:/7 ·" ,,;,{Cryptographic system available 

[ '.' ,_,_ .. •'··><"''for combined communications. 

, . . : ..,.-~~:E~iminate.s .-3rd macl_line system. ··{ .· ·'JC~···_,:·/ ~V:-~h faster tl;l.an adaptor system • 

Dis~dvantages 

Greater cost, $1677 for ECM, 

$300 for adaptor. 

Extension of ECM distribution 

renders it more liable to 

capture.· 

; 

_!!------

. [ 

... • :..t.;~¥\J .. ·.. . . . ·•' 1ADAPTOR . I 

_: ·: · - ·.'. Permits British to use Type "X" . lTwel'fe to eighteen ~onths delay · ' .. ,.

7

. -~~?JP.~ch:i.nes. , ; . 1 • · /J· before this system can be 

, . .. · +ilo,n.e ·are· riow oq board. British . II/ f.·maQ.e effective. . ·. ·.,.· . · ·. < :;'':'.'ships. · · ·""t Third system. . · . . ~ ;.'. :-~::~ Ee~atively inexpensive. ( Cryptographically inferior . ~. :,~~---,-~-<.~· 41,; - - - - tq EC.11. ~ . 

/ Mechf;Lp.;i.cally and electrically · -inferior to ECM. 

I." 

< -. '~ Slower tihe,n ECM. 

';;: ·. ' . ~:i: 

· \f., 2~ · · .!t. is reco~1mended that the ECM be made available {{ 

·.,;; i .\to our British Allies for the following reasons: 

.(a) The ECM is the finest cryptographic machine system known 

. ~- to exist at the present t.ime~ 

< ' ~ • .. .. 

·, ,.·_ 

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' • = - _.,:-
ID:A2435743 

, I. 

(cJ ' - ~ ~ . ~~· J -··- -- ~ - ·_f _.. ___ i.'~-:- ,. - _:_ 7:~~•-"7,;:<·i~~~~.~~}~~'. 

Separate code wheels and lcey lists can be issuea to our · · Allies, th_ereb~r preventing reading of U .s. traffic. ·, ... ?£ 

.::' /'/ ( dJ The ECM is~' not''the . ;fl.nil word in ·nt~cihine'·cJ:i'yp:e-og-ra.Phic ;< .~ systems. We can and will increase its security. We should, .. '":.;: .ho~ever, ·right this war using the existing ECM as our ,, primary system. 

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

. ,· ,'.: ·:·;;, · ()e') Gran tine· capture-'of 'a'll a·om.pofi'efttparts~;~-if known to us, ~ · · ~ .. ;·0·~· .. L · ;· the· ECM cannot be read by the enemy. 11-. . .... :~, -.~ - .···.rr:.. -~_. ·.·· .. _ •. - ~. •. . . - .......... ;;...,;. .... . ~ ~ - - ,,. .- --.-- ....., _ _, ; --~ ... :::_~'t~~ .. 4""··· __ -'.-- ".' --.- ·-~--·-·.~"!i.i. -;-.~~-- --.-~~=-~----- . - -

.-~ ·~j1;::·.·· __ ,--~.~.- >;'~_ .. 'J(.~·=·i~7 ~'(t) ;~e t~~Mr!~e n~;;I~~mau!tt~r~~~6!!~~h~nc1;~:n~~1~:~~ ~~:!~~~=- ~ _ tion_ problem solved in approximately 3 months. Production 

of the adaptor will require tooling-up and the consequent delay incident to manufacturing any new machine. Twelve to 

eighteen months will expire.before it can be made effective. 

;; . · :'<if :Iii c~bf ri~i'i'¥am'fi'°D'r §if6h i,;,pt,Han:ce that it ~hould bl! -~ .-;/ :~ J~ .~J?rotected by the finest system available. 

L : :'1i ;~; ~-'fii} To sup-i.~{ th~f ~i~' elt6~.f'to''°tfie'"-meximum~-

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