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SPECIAL C<m'ERENCE <A"'f ll-209 SmtJRlTY 

At&ached are minutes ot a meeting held. 12 October 1950 

at 1400 hours at the Naval Security Station, Building 19. 

Room 2.301 to discuss general aspects ot the securit7 of the 

American cipher .machine li-209, and German crypt~1c work 

on traffic enciphered by this ms.chine during World War !Io 

Declassified and approved for release by NSA on 06-10-2014 pursuantto E .0. 1352a 

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.. SPEDIAL CONFEP~NCE at J.lf-209 SJOOURITY 

Jlinutes ot meeting held 12 October 1950 at 1400 hours at the 

Naval Securit.y Stat.ion, Building 19,, Room 2300 At the invitation 

of Jlr. William Fo Friedman, Technical Coneultant to the Director1 

AFSA,, those present were: 

llr o T. Ro Wo Burton Miller 

British representative 

.llro Kenneth Lo Perrin 

British representative 

Dr o Abraham SinkDv 1 AFSA...04T 

Mro Frank Austin, AFSA .... 41 

Dro &.. Wo Pettengill, AFSA-14 

Captain Uar7 Co Lane,, AFSAc...14 

(Recorder) 

gpeaj.ng Remsrks by Kr o Friedman:: Jlr o Friedman opened the meeting b,,y 

stating that the purpose of the gathering was to discUBs in general the 

security ot the .American cipher machine H-~9, and in particular the 

amount of K-239 traffic solved by the Germans during \iorld Wa.r II and t.he 

amount. of int.elllgence they obtained therctrom.o Mr. Friedman said that the 

question had arisen during a recent discu8s1on in which the British repreaentative 1 Mro Killer• had referred to the 11vast amount or intelligence ~hich had been obtained by the Germans from the reading or tratf io 

enc17Pted "With the American cipher machine 14=20911 11 a statement the validit.J" 

of which Hr o Friedman had questioned and \1h.ich ce had asked Ur o Hiller to 

discuss with himo llro Jliller had in turn asked Jlro Perrin to gather 

information on the matter trom TlCOU aourceeo American representatives 

from. AFSA='J4 and AFSA ... 14 had been invited by Hr o Friedman to join in the 

discussiono llro Fried.man added that., although the question was largely academic~ the 1!-209 being noJ1=.0perational, he believed nevertheless that 

the discussion would prove of interest and benefit to the participe.ntso 

Remarks by Ul·~ .. Jlill..!!,: Kro lliller remarked that. tile discussion might. 

tiell have a certain amount o.f operational value, since he understood. that 

at the present time the H~209 .machine was being used for communications b7 

the U.So Arlfll" in Korea~ With the participation or British forces in Korea, 

the question had arisen or a coll!ll!On cryptographic SY"Stem t.o be employed 

by combat unit.so Whereas the British are using Typex and would be prepared 

to u.se t.he CCM at Brigade level,.the 11 .... 209 is at present. the only system. 

available to U.So forces at the equivalent U.So levelo Unless the U .. S., Arnv 

were prepared t.o put the CCK rurther forward, therefore, it appeared that 

there might ba a possibility of having to use the H--209 as a combined s7stemc. 

A discussion of its security was thus a matter of considerable interest to 

both parties at the present timeo This statem~nt was corroboraLed by llro 

Austino Mro Miller then introduced M.rr. Perrin, who had prepared remarks on 

the solution of K=209 traffic as noted in TICOK sources~ 

Remarks bz_ ifro Perrin: Mro Perrin expl.s.inE'd that he ha.d divided his 

statement into four parts: 

Ao Hol1 much M-209 traffic ~as read by the C-erma.ns; 

B. How much time \1as consumed in the reading or t.he traffic,; 

Co How v.a.s the traffic read; and1 

Do What were tbe intelligence results or the reading or the traffic .• 

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Ao flow lilUCh K-209 t.raf'tic was road bz: the Ger.maria: 

§.latsmeqt bz llro P!11•r1n: VariOtJs .figures were given by the Ge~s uho 

1u1.; e int.enogat.eei concerning t.ba amount. ot Jt-209 traffic Vfhich ttas re~ • 

.llro Perrin attir.med hie be.lief,, hOYteV'er,, t.hat. these diacropanc1es retlected 

actual dirrerencea and t.nat 'the reports,, 'While vacying, were true, since 

apparenti,- t.he armunt. or t,raftic solved differed according to the originating 

serviceo Thus, tor inst.anoo, almost. no U.S .. Naval 11-209 traffic was read: 

firatq, because t.here was lit.tle traffic, and second]3, because there •as a 

rolat1ve]3 st.rict cipher discipline in t.he.t serviaeo On the other hand.,, moat. 

ot t.he eources stated ttJat :trOlll. 6 "" 10% of u.s,, Army )[ .... 209 trat.tic 'ftae reado 

One analyst. ot the German ArlB7 Cryptologic Agency, Rudol.t' Hentze• bad boasted 

that. 30i ot K-~ tirattic was reado llro Perrin admitted that Hentze ¥.as 

poasibl.¥ an unreliable sou.rceo A German ArllJY'of'ficer~ Lto Schubert,p had 

at.ated that ll....a'.>9 tratf'ic was read tor about. 20 da.rs a montho Although t.his 

might im.p4" that tw0=>th1rda of t.he total traffic was read.a llra Perrin stated 

that the tigure presumabq related to solution of occasional keya running concurrent.~ during the month rather than to the total amount ot daily 

traf'tic enciphered, and did not therefore imp]¥ that t~o~thirds or Lhe total 

trat.t'ic had been res.do Somewhat greater success was claimed by the senior 

cr1Pt.anal1'st. of t.he German Air Force, Voegele, who said that from 6 c:. 8 days 

ot .11-.209 traf'fic on the Western Front was read each mnth by hi& unit, and 

some l - 2 day's traffic in the Mediterranean areao 

Remarks bz: lira. Austi!,l: llra Aust-in pointed out that the solution of ~raffic tor 20 days a month, provided that Schubert9s figure referred, as 

llro Perrin suggested, to the solution of occaeio.ne.l keys~ did not represent 

a large percentage of the total amo1111t ot Jl..,.Z)9 trattic pa.aaed9 since at 

somettimes during t.he war as many as 7S dit.f erent ke.fS were being used 

simultaneously, each divisJ.on and corps being provided with its own set 0£ 

ke7e,. ae were the numerous Milit.a1•7 Police battalions and units of the Army 

Air Forcea 

J&.ro Aust.in t.hen eta.t.ed that U.S.Ao monitoring of the M-209 traffic or 

an American Armored Division in England prior to D-=-Dq had resulted in the 

reading cr:ptan!J.,yticalJ.y ot 29 days' traff'ic a montho Alt.hough corrective 

meaeuree =had beei6 taken betora ths invasion. the heavy casualties a.mong 

U .So conuzwnica.tions personnel after the invasion he.cl made necessary the use 

or untrained Ar1Jf3 personnel as cr7ptographic clerks-. with a consequent 

decline in cipher disciplineo Overall estimates by Am3rica..~ experts on the 

amount of 11.~ro9 trat.ric probably read by- the Ger.mans during the war waa set. 

at io,g,, including physical compromisesa of which several cases 11.ere lmowno 

An estimate of 6% ia accepted £or the reading or ll~2>9 traffic by pure}3 ~ryptanalytic m.eanso 

Repk of l{rc. Perrin: Mro Perrin agreed in aubstanc~ ¥eit.h Ura Austin°a 

l'"emarks but set the reading or M.-209 traffic at 10% without including that 

resulting from phy'sical compromise. believing tnat the £1giire ~ith physical 

compromise innluded would be somewhat highero 

Bo How mch time waa cgnsumed in the re&diqg of t.he traffic 1 

Statement. bz Mro Perrin: Mro Perrin stated that., alt.hough there was no 

information .trom TICCll sources a.bout the amount or ti.'D.e required for the 

reading ot messa• ·es in depth6 it was presumed that this would take some two 

or three hours., There was. how~er, general agreement in TICal reports as to 

the time conswaed in b1•ealdng EJ!lative settings: this was usual:cy- aet at t"Wo 

or three hours (two hours \·.ere given by luziusj) three b.T Hent~e, two to three 

b.T Barthel. all German Army cryctanalyste) o Estimates on the amount of time 

required to obtain the abaolu.te se.ttin& varied: 12 hours was given by 

Hentze (Arm;y), lc.2 dqs by Barthel (Arl!\Y) ~ 22 hours by Voagele (Air Force), 

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72 hours bl' Schult.ze (flavy). llro Perrin sums-est.ad that. 24 hours m.ight b& 

ta.ken as an average "it one "ere lucqno Thus• a total of approximate]¥ 28 

hours would be needed atter the messa,;es "'ere received by the section 

charged with solution of the traf'fic, and it was general]¥ admitted by the 

German cr,ypt~ts that. the Jg...2)9 t.raftic was received several dqs ai'ter 

inte:iception (according to Voegele 7-B da,ys)o 

Remarks bz: at.hers: Jlro Friedman remarked that,, since cond1 tions were 

usually unfavorable,, a t.ime lag or t.wo or three weeks between interception 

and the obtaining ot the absolute settings for the Jl...3>9 trai'.i'ic would not. 

be improbablea Mro Austin voictJd the opi."lion that the obtaining ot the 

absolute set ting would require at least 1.8 hours, or mo1•e often up to 

tour &Q"e, attar the messages "Wez·e broken in deptho In support of this 

view Jlro Austin noted that. the absolute setting had been obtained bT 

U.S. crn>tanaJ.7sts in 18 hours under the most favorable circumstances; 

Jlro Austin also cited the German Ar'llf/ cryptanalyst 11 Graupe,, who gave an 

estimate ot 5 ~ 7 days ae the tin:e necessary tor obtaining the absol.ute · setting. Captain Lane remarked that the C--er.man source quoted by Hro Austin 

was perhaps less reliable than those quoted by Uro Perrin,, a remrk with 

which Mr. Perrin a.greed. 

Gene:ral Agreement: It was genera.lJ.3" agreed that the German crypt ... 

ana.]¥sts ~ere hampered b7 two factors or decisive importance in their 

solu.tion of Jl=.209 m.eseages. One was the lack of any crn>tana:cytic 

mechanical device tor tacilitating or expediting the solution, thus 

forcing all work to be done b,y hand; the other wan the time lag between 

interception and receipt of uassagee °b1" the cryptana.lyt.ic units in Berlino 

In reply to a quer7 .from Mro Friedman whether solution genera.lq took place 

at the front. or in the central unite, Yro Perrin said that frontal solution 

ot the )( .... ~9 was apparently confined to Lhe reading ot messages in depth,, 

the deter.mining o:t absolu~e settings being accomplished at the central uni&eo 

Oo How was the traffic read: 

· Remarks bz Kr" Perrin.; Mro Perrin etated that the German crypta.'lalyats 

never developed a general method of solution, although there is a description 

of a theoretical solution of the K=-209, given a text of 30<)0c.SOOO letters., 

For practical eolution ot the traffic German cryptan~sts depended either on 

depth or on operators' errors~ 

Cqrrobora.tion by llro ~ustin and Drc_P~j;.te~_!!: Mro Austin and 

Dr a Pettengill corroborated this stat.ement of Jlr o Perrin and agreed that 

the theoretical solution of tho M=.209 had been o:t no practical va.lueo 

Dr. Pett.engill added that the Germans had apparently' developed a m.eehanical 

met.hod of solutior., but the principles of this method were obecure_. and 

there was no conclusive evidence that it had actually been emp).oyedo 

Do l!bat were tqe intellig':!P.,.~~ rest!lts of the r~adin.$ of the ,trafi'i,9.: 

Remarks by Kr .. Perrin: Bro Perrin remarked l:.hat, because or the time 

lag between the in~e1'Ception ot messages and their receipt by the crypta.nal.ysts, 

the tactical intelligence gained from the reading or Jb..209 traf'fic by puroly 

cryptana.1¥f:.ic means was negligibleo Nevertheless, there was an appreciable 

amount ot strateg!E., intelligence which was gained from the reading of the 

.11.-209 traffic, such as t.b.e off'ect ot the German v .... 1 bomb_, the building of 

new air.fields) and Allied order of battleo Mr .. Perrin pointed out that, had 

the Germans been able to organise their own intercept and relrq services more 

etticientl,y 9 the solution of .14 ... 209 messages would have been of tactical. value,, 

As it was, he admitted that the value ~as main.Ly strategico 

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Remarks by Ot.hera: Mr o Friedman hereupon interposed a question as to 

the readibility ot s7stem:! ueed by the British in comparable ecbelonso 

Mro Perrin stated that the British equivalent systemb the Stencil SUbtractor 

(SS) Frame, was never read bJ' the Germans except for ona month 'l'fhen the 

basic book had been capt.ureda Dr. Sinkov remarked that the British cipher 

had two dieedvantagee from. the American point ot vie\ilo One wae the 

cumbrous nature of tlle syat..em.; the other Yl&B the tact that Am.arican operators 

are not trained in sending or cop.Ying digits,, and thua.. tind a s,ystem like the 

SS Frame ditticW.t to usea 

Jlr" lliller added t.hat. the Stencil Subtractor F.rwne had also been less 

uaed than the American J&=.209, eince the British cipher machine i)pex was 

used e.t a lo~er echelon than t.he cOJRparable American device. and thus 

'l)'pex relieved the stencil Subtractor Frame or some 400 ... 500 messages dail.70 

llro Austin corroborated Mro U:l.lleroe remarks and stated that. t.he U.Sc ArJJJ¥ 

was so organized that the bulk 0£ regimental and combat level trattic was 

necessarily" encrypted with the )l ... 2090 

Q.oncluding Remarks bz. ~o Frie~ and lire Mille,!:: 

Re-statement ot Matter at Issue~ Following a. b1•ie1' summary of the 

discussion by Hr., Friedman, lira Miller stated tha.t the matter at issue 

concerned the remark he had made that "a vast amo1mt ot intelligence had 

been obtained from. the German reading ot the American l!.-.209 JP.s.chine 1•,, and 

it was now a question of "Whether in tne light or tJse discussion he should 

withdraw his et..atem.ent in whole or in part or ''hether he would de.fend ito 

lire Miller considered t.ha.t he should withdraw the P.ord nvastn and 

asked that the tollolfing statement be substituted.: 

"Disregarding inf orma.tion obtained .trom the use of captured ~209 k.a;y 

lists,, it is generallJ' agreed that a considerable amount of American Jil=.209 

traffic was broken by the Germana during World War II, from which little 

tactical intelligence \1as deduced, but from which an appreciable amount ot 

strategic intelligence waa obtainedo It ia .further agreed tha.t, due to the 

inetticiency of the German intercept organization, the lack of modern 

eryptanazytic machinery. and the failure ot the GerJl'o.ans at high levels to 

appreciete the value or speedy intercept, for~arding, and processing ot 

traffic,, the German success did not represent the max.in.um. potential 

exploitationo 11 

General agreement: The above otatement was ;...greed upon by all present 

a& representing a tair and reasoned resolution or the matter at iasueo 

Potential Usefulness ot the Discussion; It v1as agreed that a rec.Ord 

ot the discussion should be made, and that such a reco1•d might be usetul tor: 

(a) Future Briti5h=American discusaione as ~o the use of the CCll at a 

combined Army echalo11 lower th.an that at which it 1.s presently used; 

(b) Background as to the possibl.e solution by potential eneiey agencies 

or systems such as the Jl ... 209 and comparable British systems; 

(c) A source ot reference for discussions pertaining to the proposed. 

improved Hagelin device and its possible solution by cryptanalytic 

means; 

(d) A record ot inte11 est in it£>elf' which should be added to the 

pertinent operational and historical records or the participating 

Agenciese 

Approved: 

T. 1i.. w. Burton Jliller