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September t, 1919. 

C:.'lbe Militar)" l~~el1igence Div!s~on and the Signal Corpe have 

gone ove.r the e.xp~ei tion on tQe A. 'l'. and 'l'.. C~m.pany cipher machine 

enclo•ed Yi.th JOUJ' letter of August 21st~ I .wish to express t~ 70u 

my •PP~f.eoiation ot the interest you have taken in this matter, and 

to pe~ut. tut .aoJr&e qt the niore ~portent preuaiaea that you have 

contused. · 

Yo\1 az>e cor.rfJct in rour etatement in paragraph 3, page 4, that 

the .\mGqU:itl .shif ... in,g Of tap08 af teJ" 88.Cb $08BGg8 mq roeul t ill 

•an ov•r lap,n, b,ut this is tru.e only provided that A :tape is ehitted 

, .. ,..:>;:':-s;;.~:. :; · ta.rther torn.rd .th•· B te.pe, a· 11~tho4 that the Signal Corps has 

l ,-·· · r.- · ---·-· -always avoided •. 'lbe Signal Corpe meth.od conoists in always adding 

1. ~ , to the. 8 t~e one o:- lllore t'lum'tlet's ftlO:re than the nurnlJer added to the 

i· ; ·A :tape • . . _, . I ... 

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. . Ref erring to 70\lr et•tenu»lt in paragraph 5, pago 5, s, ft i• A tape instead ot I "po that i• used u a 'b•His tor liai ting th• combinations 

•o ~ u,ed by ditter-•nt. fJt$iions. It 1.s ne·oes1a.r1 that each station . ltegin .t.h·e day's l>.ueinees "•it.bin bounds".· 'b.._t tbs op~.rator. never could 

· be ~out ol boundsu, in case of there being four ata~ione, until he has 

sent ·enQugh. message~ to uae ~p one ... qu~ter of ihe total possible 

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· cpmbinat4.ona.. '!he ditt.ere:noe between thf.I two .Qipber indicator& m&y be 

as g,reat .~ the length of thfil longer tape inata.tt of buing limited as 

outlin'd in. yo~r m•orandum.' · 

'lhe confusiQft concel"l\1ng. the meaner of shitting tapes between ~eosagas outlined in paragr,aphe 1. and 2 on pag•:1 •hquld be cleared ~Y 

the'f~regoing. Begtnning 'lithin botU148, each atat,on after the end of 

each message n$ed only add an arbitrat.J number of. 8111 ei1e to 8 tape 

only or to bo~ .A and B tapes, e•cept ~at A ~ape is never shifted 

ro..,.ard more :than B tape. 'lb~a• ara the only ~eatriotions. 

[11b- ~olutiort outlined in your taemoran.dU!!'l ap.peare to depend upon 

so many corr,ct gueasee of .tH~ unknqwn, ae well:aa upon a coincidence 

o! e1cles 1 that I feel that the onl7 eatisfeotOJ')' adJuetment of the 

entire matter ~s tor JOU to accep~ the plan. oqtlinad in General 

Gq\lier' a telegram to 1ou of Augus'tt 28th·, in which h• eta-tea that the 

ciph.er machine is in operation and that \he Signal Corps is prepared 

to send as test messages an actual day's business from their tiles. 

'fe · cannot question General ~u:ter• .a einceJ!'e interest in this matter 

and the-meeeag•a which will be aubmitted to you will, of course, have 

no trick encipherments • .:J 

@'pp roved for Release by NSA on 11-18-2014 pursuantto E .0. 1352a 

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REF ID:A414BBB6 

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. [1 ·Shoulct liko .~o ad.d .that as. a. resul '\ .of 7our inveati.iationa 

o.t the ~. T.~. and T. ~iph.er. •• have submitt-e4 '\o the Signal Corpe methods, tor diaguiaing ~ cipher indica,tors, 1lhich •ill make 

impossible .;ijle .8.t'rang.emen.t .of the .usaJig~HJ .in oorreqt oyclee. such . a11 arr:a.ogaaent .it .. the .i'ira.t .~d easiantial. st.op in .U\e mothode of 

sql;.uUon that . .y_ou. h~Ye pq:lnted ou.t ·to ua:.::J. · 

. • . I .11,i.ah 'to :e~ree.e .:t,o_ 70.,,.. my. de.ep .. epp.re.oiatltxt tor your intereet 

in this ou'bj,act ,. ~d to ueure 7ou tha" both the u. l.. D. and the , s.,e. are .an:xio.~e (or $JU'. addi,tional in:formatlon ..t\lat )'OU mar develop 

in the tuture • 

.. .. -........ . .'-~ ..... - ' . ~Very aincerelf youra, . t t 

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!AlLEDL~!la B.,G.s. SEP 2 1919 

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