Copy No. J. 

LCS(53)/S/Report (Final Draft). 

UK/US COMMUNICATIONS SECURITY CONFERENCE 1953 

REPORT OF THE SECURITY SUB-C01v!MITTE"E 

to the 

"EXECUTIVE COlVIMITTT!.'E 

1. The Security Sub-Committee has ma.de security assessments of U.K. and U.S. 

systems which are attached at Appendix A. It should be noted that the phrase 

"further study required" as applied. to an equipment still under development 

means tb.at information is insufficient fqr a final assessment but that 

continued development is justified. 

2. Recommendations on transmission security are attached at Appendix B, 

3. An agreed method of expressing security assessments is attached at 

Appendix C, togetHer with proposals for the information which should be 

provided by users in stating their requirements from the security point of viev~ 

Because of the nature of the discussion in this pa.per the Security Sub-Committee 

recommends that only the following statement be.included in the main report of 

the Conference: 

"During the Conference the u.K. and u.s: security advisers 

prepared an agreed method for the technical stat~ment of 

security assessments. 11 

4. In addition the Security Committee has the following general 

recommendations to make:-

a. A high priority should be given to a thor~ugh investigation of: 

(1) the properties of quantised speech; 

(2) the practicability of intercepting, recording and countii:ig 

the output of many of the speech equipments under 

consideration. 

b. · Steps shoul~ be taken to replace as soon as possible equipments 

employing an additive system in .such r5.-way that there is a 

significant danger of producing a readable depth of two. 

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c. Only one-time key tape which has been produced and checked in 

accordance with agreed Ul\l'US standards should_ be employed with 

one-time tape equipments. 

d. All equipments shou~d be rendered secure against spurious 

emissions which endanger communications security. 

e. The design of on-line ~quipments should be such that it is 

impossible to transmit plain text ine.dvertently in place of 

cypher text. 

f'. Further study should be ,made of keyboard operation with start/stop 

on-line teleprinter cyphering systems to analyse the dangers 

arising from operator and machine idiosyncra.cies. 

g. The cypher signal transmitted from-an on-line cypher system must 

be a pure cypher sig:n.nl not containing any elements recognisable 

as plain°text or cypher key. 

h. The cognis~nt authorities should be informed of the UK/US views on 

the security of the S.I.F, with I.F.F. 1\iiark X. If a solution to 

this problem is to be found it is essential that the users should 

state their overall security requirements for an I.F.F. system. 

5. The Security Sub-Committee also offers the followlng recommendations to 

impr~i:iso:n ~etween ~·. --4--~~~M.\<:_ ~~ LJ {:) ' t\("~.l. ~UJL ~anc:r~u PL 86-36/50 USC 3605 

a. An exchc.~nge of working cryptanalysits between N. S. A. li-1 and 

~ G. c. H. Q. q the details to be worked out between N. s. A. and 

G.~ ---· 

-tr.1 ~addition to 

. ~~-&L. this exchn.nge of p~rsonnel, ~s~ug;at visits between 

U.K. and u. S. for _the!f'6'!i@;Ro techniool discussions of communicat.ions 

vi .l.M~\l ~d,.. ~ ,. securityf> ~U\J~ ~he ±i&ermnl ta.lks. a.wLPbose I a.tag.as 

¢ fpture OOMSEC Conferei:iaes ...Q.i;tl shrn1l d not precl.rn).,,, tw"' pres@nce ot:.. 

f:f5tCa1.Lt;y a~k~s at future Phase II t~rpe Q~Rfer ..,noes. 

/c. 

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. ~ .l1. more rapid interchange of new information and ideas 

. nffecting systems urder assessment and questions of 

transmission security. 

C;,. Tho preparation of an agreed progrrunme of cryptographic 

assessments for the coming year; this prograi-mne to include 

both U.K. and U.S. systems which require assessment; N.S.ll... 41 

to prepare a draft programme of' this kind and f orwn.rd to the 

C.P.B. for agreement. 

PL 86-36/50 USC 3605 

Chairman 

Security Sub-Committee (Pruise I) 

3rd November, 1953. 

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0<?,i?l No. C I· 

.APPENDIX 'A1 to the Report of 

the Security Sub-Committee to 

the Executive Cammi ttee.: 

UK/US Co:t'll1'IDNI~.i~TIONS ff~CURITY CON.B,ERENCE 1953 

SECURITY i~$SES.SMEN'"f OF CRY.FTOGRil.FfilC EQUil"Mff:NTS 

IN USE AND UNDER DEVELOPME11T 

1. Off-line Equi~ments incluaing Teletypewriter Equipment . -··· tj 

used. off-line. 

2. On-line Teletyrewri ter Systems •. 

3. Speech n.ru::1 Cifa.x Equi:pm.ents. 

4. Svecial Pur2ose and Hand Systems. 

5. Cryptographic I-reduction Equipments.· 

30th October,· 1953. 

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1. Off-lino Equipments: Tclet¥Pewriter Equipment used Off-line: 

Special .t"Urpose System 

a. U.S. Equipments 

( 1 ) .. ·i.FS.t1.M D. 17 

(a) The U.K •. require further study. 

(b) The U.S. consider that with clear indicators the system 

is secure for low echelon traffic. · · 

The U.K. and U.S. consider· that the equipment is secure subject 

to adequate checks of the standard of the one-time key tapes. 

( 3) .i\FSii.M 3 6 

(a) The u. F;. consider that with ad.equate precautions in the 

choice of machine set-up, with bisection and with message 

lengths restricted to 250 letters the syst~n is adequately 

secure for low echelon use. 

(b) The u.s. consider, that with th~ limitations already 

placed on it, the machine is adeqU'.ltely secure as a low 

ecelon systei:n but they >vill examine t~e U.K. limitations 

in detail. · 

( 4) .AFS.AM 7 

(a). :POLLUX 

(i) The U.K. ~re not in favour of ·clear indicators because 

of thG possibility of recognising awl exploiting 

tail.ing messages and. mes.sages in depth. Further study 

required when more is known about traffic loads and the 

likelihood of o~crators 1 errors. 

(ii) The u.s. c·:msider the ~yste~ adequately secure for low 

echelon use but. they will keep traffic under review. 

If dangerous insecurities appear they feel tha.~ they 

can modify the proceJurcs sufficiently to overcame them, 

(b) .iillONIS 

(i) The u. K. consh~_er that l:..DONIS is secure for all 

classifications of traffic for at least the next ten 

years pr~vided that a good standard of operating is. 

maintaine•l but require further study in view of tho 

recent increase ~n the numb~r of elements. 

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(ii) The U.S. consider that .ti.DONIS is secure for all 

classifications of traffic for the next· twenty years 

provided that a good standard of operating is 

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( 5 ) ~)]'Sii.M 4 7 ( BRU"rtJS ) 

The U.K. ari.cl U.S. consider that the system is secure for all' 

clnssifioa.tions of traffic for at least the next five years 

i_.)rovided. that a gocxl standard of operating is :qiaintained. 

(6) CSP 888/889 (HERCULES) 

The U.K. and u.s. agree that the BERCULES system is secure for. 

all classifications of traffic for the next five years provitied a 

good stan:Jard of op0rnting is maintained. 

(7) c.c.M. (LUCI~i!JR) 

(a) The U.K. and U.S. agree that LUCIF.b."'R gives adeqU.3.te security 

for all classifications of traffic for not ~ore than three 

years provided tho.t a goou standard of operation is maintained, 

but consider that the c. C.M. mus·t be replaced as soon as 

poss;ible. 

(b) For 11!fet0/orologica1: traffic, the U.K. and U.S. n.gree 

(i) that it is not essential to have separate rotors for 

meteorological messages provided that there are 

separate key lists. 

(ii) that in ship-to-shore systems short meteorological 

messages can be incorporated in ordinary messages. 

(8) SIGTOT (Off-line use) 

The· U~ K. and u. S. agree that the system is secure f·:ir all 

classifications of traffic subject to adequate checks of the 

standard of the one-time key tape· and provided that effective 

physical methods are employed to prevent the-re-use of key tape. 

( 9) ~\Sl~M 2-1 ( OROUS) 

(a) The U.K. believe tho.t the indicator system may be vulnerable 

and if' this is so the machine set-up for _each link using the 

srune key pad can be recovered. Further study is required 

when det::i.ils of traffic volume an:1 message lengths ara 

available. 

(b) The U.S. believe that the volume of traffic encypher,ed on 

one machine is too little to make this a serious shortcoming 

but also requires further study. 

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(c) Tho U.K. and U.S. o.re concerned however at the insecurities 

which may arise as a result of operator's errors on-:l agree 

that the procedure, being one which permits of a 

significant clanger of producing a readable depth of two, 

shoul-1 be replaced. 

(:1) The u. K. and U.S. o.gree that the machine should be 

replll.ced. as soon as possible. 

b. U.K. Equipments 

(a) The U.K. regard the system as a1equately secure for low 

echelon use for the next fifteen years provided that 

(i) tho number of groups encyphered at each indicator 

is limited to 50 groups, 

an::'!. (ii) indicators are extro.cteJ. from specially constructed 

key lists. 

For higher level use indi~~tors must be disguised 

( encYPherod) am..=!_ messages limi. ted to 50 groups •. Even so, if 

it is necessary to legislate for the undis9iplined operator 

PORTEX cannot be guaranteed as adequate for TOP SEOR~T 

tra.ffic for more than the next five years. If the rules are 

observe''!. and assuming an a::l.equate in".licator system, tho 

ma.chine mFJ..Y be regarded as secUX'.e for the next t·wenty years. 

The U.K. consider :i:ORTEX to. be a Category '~' cryptosystcm. 

(b) The U.S. require further study. 

( 2) ~Yl.1JX II. ( SI1'1rt'lliX) 

The u. K. an:l U. 8. agree thn.t the system can be regardeJ. as 

adequately secure for the next five years for all classific~tions 

of tr~ffic proviaed that 

(a) a 600d stanili:>.rG cf operating is maintained, 

(b) bisection proce,lure is used, 

( c) the variable spacing usec.1 is of the 1 ' 2, 3 type. 

(3) T.Y!-:5X Mii.RK 22 

(a) The U.K. consi~er the equipmont.is secure for all classifica.-

.tions of traffic for at loo.st the next five years. 

( b) The u. S. know nothing ai;ains.t the system bu_t require further 

stu::ly. 

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(4) SINGLET/PENDRAGON/COPPERFIELD (UPSTART) 

The U.K. and U.S. know nothing against the system but 

require further study. 

· (5) ROCKEX 

The U.K. and U.S. agree that the system when used correctly 

is secure for all classifications of traffic subject to adequate 

checks of the standard of one-time key tape arid to further study 

of spurious emissions which endanger communications security. 

c. Miscellaneous Equipments 

c 1) .__I ____ ___. 

E:03.3(h)(2) 

PL 86-36/50 use 3605 

(a) 

(b) 

.__...,....,---=--!I Adequa.te security for low echelon use could be 

achieved by the use of a codebook provided that no spaces 

are encrypted between groups. 

The U.S. require further study as a matter of urgency in 

view of the U.K. statement. 

(2) CX-52 and CX-52H 

The U.K. and U.S. require further study as a matter of 

urgency but there seems little doubt that it will give a very 

high degree of security if properly used. 

2. On-line Teletypewriter System~ 

a. U.S. Equipments 

(1) AFSAM 9/AFSAZ D7315 

(a·) ATHENA 

The U.K. are not in favour of the use of clear 

indicators. 

The U.S. require further study as to the extent to 

which clear indicato~s can be used on higher level nets but 

consider that clear indicat0rs are probably acceptable on 

low echelon nets. 

The U.K. would approve the use of AFSAM 9 with AFS.AM 109 

with encyphered indicators for all classifications of traffic 

for the next five years provided a reasonable standard of 

operating is maintaineda During the period a very_ careful 

investigation should be made of the occurrence of operatorst 

errors. If operators' mistakes are such that any of the 

attacks appear dangerou..~ the U.K. sugge~ts that the machine 

be modified by t~e addition-of a plugboard. 

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(b) AENEAS 

The U .• K. a:nd U.S. agree that the system is secure for 

all classifications of traffic subject to adequate checks of · 

the standard of the one-time key tape. 

( c) PYGMALION/IRIS 

(i) The U.K. view is the same as in the case of AFS.AM 9 with 

AFSAM 109 with oncyph.erred indicators but they are also 

concerned about the loss of traffic flow security if' 

indicators are chosen at random. 

(ii) The U.S. consider the systems will be secure for all 

classifications of traffic if properly used, but after 

experience of the machine under operational conditions 

they may have to revise the procedures. -They c..onsider 

that operators' errors can prejudice suourity but they do 

not expect them to occur sufficiently frequently for 

there to be any danger of compromise. 

(2) ASAM 2-1 (DAPHNE) 

(a) The U.K. and U.S. agree that D.APiiNE procedure is adequate for 

on-line or off-line use. The achievement of security of 

traffic passed by D.APRNE procedure requires the modif'ication 

of the associated equipment, where necessary, to eliminate 

the possibility of operators' faults which may cause 

inadvertent transmission of plain text. 

(b) U.K. and U.S. agree that the ma.chine should be replaced as 

soon as possible. 

(3) .Alt,SAM 4-A (CENTAUR and IXION) 

·(a) U.K. require further study. 

(b) U.S. accept CENTAUR and IXION procedures but will review the 

indicator procedure for certain uses. 

( l1-) .AFSAM 44, .AFSAM 45 

U.K. and U.S. agree that the system is secure for all 

classifications of traffic subject to adequate checks of the 

standard of the one-time key tape. 

(5) SIGTOT 

U.K. and U.S. agree that the system is secure for all 

classifications of traffic subject to adequate checks of the 

standard of the one-time key tape and subject to a modification 

of the associated equipment to prevent inadvertent transmission 

of· the plain· text. --

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( 6) ~i.FS/i.M D9 22 

(a) The q.s. consider the machine secure f'or all classific..~tions 

of traffic. 

(b) The U.K. require further study. Not:qing known against. 

( 7) .;i.FS.AM D. 26 

U.K. and U.S. require further study •. 

( 8) i&SiiliI D. 3 7 

U.K. and U.S. require f'urther study. 

b. U0 K. Equipments 

(1) MINSTER 

u. K. and u. S. n:::rted tlnt the U. K. Services do not intend 

to use this equipment .. 

( 2) MlllTROi.-:OLE 

U.K. an~ U.S. require f'ur~her study. 

(3) I HILOM."EL 

U.K. and U.S. require further study. 

(4) CONVERTOR NO. 5 

. U.K. and U.S. agree that the equipment, when used with 

.Apparatus 5 u.c.o., provides adequate security for all cl~ssifications of traffic for tho next twenty years. It is 

believed that complete traffic flow security will be provided; 

further study will be macle to verify this. 

( 5) ~\.RT ICHOKJ1J 

U.K. and U.S. agree that the equipment provides adequate ~ecurity for all classifications of traf'f'ic f'or the next twenty 

years. It is believed that complete traff'ic flow security will 

be pr::>videJ.; further study will be made t"o veri£y this. 

( 6) iL;:T:ll.RATUS 5 UCO 

U.K. and U.S. agree that subject t".> adequate checks of the 

standard of one-time key tape the equi:i;iment is seeure for. all 

cJ.a.ssifica.tions of traffic. 

(7) CIRCUIT 11ERCURY 

_U.K. and U.S. agree that tho equipment is secure for all 

classifico.tions of traffic for at least the next twenty years. -

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( 8) INCUBi .. 'COR 

U.K. and U.S. require further study. 

3. Speech and Cifax E1ui?ments 

a. U.S. E~uipments 

(a) The u. s. consicler the system is secure for at least the next 

five years •. 

(b) The U.K. require further study, since the number of variables 

in the system has- been increased. 

(2) i£FSii.Y D. 809 

u. K ... and u. S. re'-_;,uire further study. 

(3) .AFSJ~Y D. 807 

(a) U.K. consiner that if D.807 transmissians can be interce?ted 

and recorded, the :mo.chine cannJt be rega.rclerl as secure for S~CRET traffic.. The_ technical difficulties Jf intercepti~n 

and rec~rdin13 a.re a.t present so great thP.t they add 

considerably to the security ·Jf the system. . 

(b) U. s. consider the mach:i,ne secure for all classifications of 

traffic subject to further investigation of the possibility 

of intercepting :ind recording or counting. 

( 4) J'i.FSJi.Y D. 808 

U.K. anl U.S. reiuire further study. 

( 5) ,"JPSl~Y D. 81 0 

u. IC. and U. S-. require further st~dy. 

( 6) .ii.FSli.Y D. 81 6 

(a.) U.'K. consider that if D. 816 transmissions can be interce:i_.)ted 

anQ counted, the equipments cannot be regarded as secure 

even fJr Secret traffic. 

(b) U.S. re~uire further study of U.K. views. 

( 7) .1.iFSAY D. 801 

U. K .. e.n.i U.S. req_uire further study. 

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( 8) 11."FSJ.i.Y D. 804 

(a) The U.K. view is that the system without random walk rings 

cannot be considered to provide the ctegree of security 

re~uired. Further study of systems with random walk rings 

is required. 

(b) The U.S. consider that the system without random walk rings 

but with apprQ~riate alanns is secure for lQW echelon use 

although they recognise the possibilii:;;y of successful high 

speed attack. The U.S. consider thB.t the system with random 

walk rings and alarms is secure for all classifications of 

traffic. 

( 9) .i.FS.."i.Y D. 830 

U.K. and U.S. agree that the system is not secur~ and d:> 

not recommend its use for any purpose. 

The U.K. and U.S. agree that the equipment is secure for on-line 

cncypherment of facsimile or telety-~e for a~ least the next twenty 

years. The U.S. will carry out experiments to verify that adequate 

traffic flow security will be provided in multi-channel -

telctY?ewritcr use. 

( 11 ) Li.FSii.X 503 

U.K. and U.S. agree that the equipment is secure for all 

classifications of traffic f-Qr the next twenty years. 

(12) ~i.FSJ:JC D.505 

u. K. and U. s. require further study. 

b. u.-K. "Equi-pm.ents 

( 1 ) Bli.NGL"E 

(a) U.K. and U.S. azree that the equipment is secure for all 

classifications of traffic subject to adequate checks of the 

key film ana provision of satisfactory alanns. 

( 2) SORCERER 

U.K. and U.S. agree that the equipment is secure for all 

classificatLms of traffic for the next twenty years. 

(3) BLUE BOY (D. 70) 

(a) The U.K. view is that because of practical difficulties of 

interce:pting aml recording, the Apparatus D. 70 which includes 

the key generator BLUE BOY, may be considered as secure for 

a period of at least five years. It is still under study. 

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(b) The U.S. re~uire further study. 

(4) ~RUMl~TER 

U.K. and U.S. require further. study. 

( 5 ) Hil.LLM."l.RK II 

U,K. and U.S. require further study. Y~re experimental 

data on the properties'of speech in delta modulation systems are 

required before a final assessment can be made. 

( 6) PICK'lICK 

U.K. ana U.S. require further study. 

( 7) MOUNTEB/i.NK 

(a) U.K. c:::msider the equipment is secure for the next twenty 

years. 

(b) U.S. require further study. Nothing knovm ag~inst. 

4. Special Purpose Systems 

U.K. and U.S. require further stucly in the light of the 

possibility :if planned interrogation by an enemy. 

b. ..i..FS.ii.M 498 

The u. K. and u. S. agree that the machine is theoretically not 

secure against planned interrogation by an enemy. 

c. ,,,:.J,i'Sl~.M D. 31 

The U.K: and U.S~iagroe that the system is secure subjectto 

acleq_uate checks of the. standard of the one-time key ta:;_:Je, 

d. :Nl .. T'EX 

t 

(1) Security 

(a) The U.K. consider that with the restrictions already 

suggested by them the NATEX. cryptosystem with underlying 

plain text is adequately secure for ail classifications of 

traffic but there is some danger from cribs and operators' 

errors. 

(b) The U.S. consider that N.'.T"~X with underlying plain text is 

secure as long as certain restrict_i9r:tS are im:tiosed, but ' 

require further study on the exact nature of the restrictions. 

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(c) The U.K. and U.S. ag:r;-ee that the use of an underlying codebook 

would have considerable security advantages and_Jnake some of 

the restrictions unnecessary. 

(2) Indicators 

(a) The U.K. and U.S~ agree that for general NATEX use it is 

desirable to have a new five letter indicator system which 

would enable the message to start at any-position on the line. 

(b) The U.K. and u·.s. agree that the indico.tor system proposed by 

the U.S. be recommended for N~TEX 3rd level use with the 

following modifications: 

(i) identification of the indicator page to be from message 

externals only, 

(ii) operators to be forbidden to choose the six letter 

indicators from their assigned page in regular order. 

e. Running Ke.r C,y::eher (u.s! MERCURY} 

(1) The U.K. consider that if plo.in language basic text is used with 

R.K.C. in quantity or with any regularity the system is not secure. 

Provided, however, that a well constructed basic book is used, 

security is greatly improved, but it cannot be guaranteed that 

exploitation of an occasional key table will never be possible. 

The U.K. consider R~K.C. to be a Category B system. ~ 

(2) The U.S. generally agree but require to study further the U.K. 

views particularly on the Category. It is now in existepce as 

a Category 'A' system. 

The U.K. and U.S. agree that the system is not secure and do not 

recommend its use for any purpose. 

g. Double Subtraction on S.S. Frame 

The U.K. and U.S. agree that the system is secure for ~11 

classifications of traffic provided that different key sheets are used 

for the t:wo subtractions and that the agreed safe· traffic l'Jad is not 

exceeded. 

h. I.F.F. System (High Security Identification) 

(1) the U.K. require study. 

(2) The U.S. consider that the system is m.argir??-lly secure but it can 

be improved by the addition of"another permutation. 

i. s;r.F. with I.F.F. 1fark x 

(1) Mede 1 

The only cryptographic features of S.I.ll,. with I.F.F. Mark X 

are the methods proposed ~or providing the changing codes in 

Mode 1 operation. Even if the meth0ds of changing the code were 

/cryptographically 

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cryptographically secure, the U.K. and U.S. ugree that it is not 

possible to change the code frequently enough to prevent the enemy 

from masquerading. In addition, the risk of physical compromise 

of the cryptographic element is great. The U.K. and U.S. 

therefore agree that the use of S.I.F. vrith I.F.F. M".ark X on 

Mode 1 with or without any code changer is an insecure method 

of proving an identity.· 

(2) Modes 2 and 3 

No cryptographic security is proposed for-Mode 2 and 3 use 

of S.I.F. with I.F.F. Mark X and the U.K. and U.S. agree that 

these functional and personal identity modes could be a-most 

valuable source of intelligence to the enemy. 

(3) For the reasons given above the U.K. and U.S. agree that the 

whole of the present programme for the use of S.I.l!,. with I.F.F. 

Mark X should be reconsidered. 

5. Cryptographic Production Equipments 

a. JIFSJ~W 7200 

The U.K. and U.S. agree that subject to satisfactory results 

from zero increment counts and from all standard checks on individual 

tapes, the tapes produced by .AFSiUV 7200 can be considered adequate 

for all types of use. 

U.K. Equipments 

b. 5 UCO Key Generator 

The U.K. and U.S. agree that subject to adequate checks during 

and after production the tape produced •by the equipment is secure. . .. 

c. ROCKEX Key Generator 

The U.K. and U.S. agree that subject to adequate checks during 

and after production the tape pr0duced by the equipment is secure. 

d. BANGLE Key Generator 

The U.K. and U.S. agree that the key film is probably secure 

but further study is required because of a small bias which has been 

detected in the key film generator. 

e. TRIMMER 

The U.K. and U.S. agree that further study is required but, 

subject to adequate checks of the output, the key produced is 

probably secure. 

/f. 

TOP SECRET 
< - REF ID:A52292. 

TOP SECRET 

... 12 

f. U.K. HOLLERITH Methods 

U.K. and U.S. agree that pads produced by this method are 

secure provided that adequa~e supervision is maintained ·during 

production. 

g. U.S. Pad Production Method 

U.K. require study 

U.S. consider that pads produced by this method are secure. 

NOTE: A check of a production equipment or its product is considered 

adequate it' the check is designed to meet agreed UK/US criteria. 

TOP SECRET 
REF ID:A522923 

eTOP SECRET e 

1.P.i?ENDIX B to the report..Ef.._!h!:. 

Security Sub-Committ~~ to the 

Executive Committee. 

COPY NO: 1 

UK{us COMMUNICi.TIONS SEClrRITY CONl!1BRENCE 1953. 

1. ?resent Srtuation. 

SECURITY SUB-COMMI'rTEE ~£ORT ON TRANSMISSION SECURITY 

The u.K. and u.s. agree that British and U.S. measures to maintain 

transmission security do not reach the same standard of efficacy as do those for 

the maintenance of cryptographic security. ?.z-eaent practices a.re insufficient 

to deny a potential enemy intelligence derived from the study of elements of 

-

transmissions external to the cypher text. 

2. Contributory Factors. 

There ore a number of inter-related communications practices end methods 

which contribute to this state of insecurity; these are discussed below: 

a. The Use of Plain Language. 

The ~~ use of plain language for the tran:smission of messages, even 

those in themselves unclassified, not only leads to revelation of 

intelligence but tends to nullify the good that can be achieved by 

otherwise sound security practices. This is true for two reasons: 

because -compilations of individual "unclassified.items 11 of"ten provide 

intelligence of Secret or even Top Secret classification, and because plain 

language messages, related externally to cypher mess~es, can jeopardize 

the security of "the latter Bn:d of: the address procedures employed with them, ~ fk ;;r.:....,' y.~~.J· .. t . The U.K. and U.S. ~ree that- redio tran~missioneof/plain langu~/mesaa.gea 

should be forbidden, regordless of whether classified or not, excepting 

cases covered by the alrearly agre~d prcvis")~ in toctical ·s~tua.tiona. ~ 

_ p.0ffllll!'ind11Ig off'ieilr IDfl;¥ authorize the s.endiJ;lg ~r messagQa l:a tre==e:leaT.- , . 

b. The Use ::if Plain Language .Addressing on Encr;ypted Messages. 

The use of ?la.in language addressing on encrypted messar;es leads to 

provision ~f direct intelligence of the order of battl~ tYPe and also to 

possibilities of e~suming with fair accuracy the conten"t cf certain of the 

encrypted messages so headed. The U.K. and U.S. agree that "the use of 

TOP SECRET /plain 
844 ... •--

.- • 

-~+ 

... 

plain language addressin~ on classified messages shouln be 

abolished. 

c. Call Sie;ns. 

Cail Sign Systems used by all stations other than the large 

fixed ones which must inevitably be identifial:>le, must be secure against .. . . 

the enemy tra.cing the conti:nui ty of identity f-rcm -da,y tc da;y. ls.t 

present there is nc. universal means for.providing this call sign . . ~ 

security e..lthough there -is agreement on -"J:;Jle _uae_ bf daily changing call 

signs in time cf war. The U.K. and U.f:> .• have· examined the basic cal..l 

sign systems and the "call sign ·enc~y.?ti:.m: pl~:i:i" ~ agree the folkwingt 

- (1) Daily changing calls shr)uld be· institute~ _in time of peace. 

Their value lies not only in t~- 1.ntel_ligence they deny the 

enemy but in meking har11er er imp-::ss~ib~.:.; 'his task cf 

maintaining continuity of identificati.:;n 'ft·:)m peace to war. 

(2) New basic books shciuld be pr~dticea· i::..nd sh6U:Ia ~e oc-mpi?-ed 

with properly hattecl vari@ts. 

(3) '.rhe use of G. comm'm cell si:gn encryption key list i'cr all 

Services world-wide has cons;i.derable_- s_ecurity llisa.dvantages. 

(4) The overall rule~ua.cy of the current system for the encrjrption 

of call signs should b~ reinvestigr..ted and: if necessary a ne:w 

one ·devised. imy new syst0m for call sign encrypti~n, in 

a.dditi.:m to be:j,ng seCU.re ~ even with the basic bock ccmpromised, 

must be easy to use e.nd to prcciti:cs9 

d. It1reguency Chanp;ing. 

The U.K. e.nd U.S. agree a. means must be found to change 

frequencies at a rapid rat8 and.~th wide variatio~~; that failure to 

do this will t.end t:, diminish the security e.chiev~ble by the other 

practices under discussir.:n. 

e. External Chcracteristibs of Cryptcsystems. 

. . -

The U.K. and U.S. agree that the fact that crypt.:1systems can be 

so~ted intc' general types by external characteristics, ana intc specific 

tYl_?es by sys"tem indicators (rliscriminants) is a S(,urce of inaecuri ty 

that shc?uld be elimine.ted. -

TOP SECRET /f. 

·--...- r-

·+ ··-""-· 
~~~~---~--~~--~~--_~~--~~---~~-

... .,· 

~· • 

REF ID:A522923 - . e 

•ror SEalll 

f'. Jmthenticaticn. 

The U.K. and U.S. agree that the currently approved systems e.nd 

methods for authentication, although_ secure in many respects, do not in 

fact af'f'ord a guarantee of the authenticity of tr~.nsmissions or -a 

positive saf'egur~d against intrusicn. 

g. Message Externals in Tape Relay. 

l:'resent tape relay systems cannot operate without undisguised 

routing indicators. The U.K. and U.S. agree. that. uncl.isguised routing 

indicators provide valuable intelligenqe, ~P. tl;i~~-. their. ~ t"ransmission . . .. . . . .. . 

over radio and sensitive line circuits must' be elimill:atea.. ~, 

pr~sent ta:pa reley procedlires reqcr±f'e a ~SBie s1iri'rhmu. The u.K. and u.s. 

~ II~ "'"'~t-p\_. . .·· .- .: . . . agree that tl:!"fL~la- ~hwet.lJr,_.appe8Fs. to.be the adoption cf· 

- tM 1\.L,e t ~""'~ ~ -£:~ w~- totai link encryption using cryptosysterns· capa.ble~Y:~iding "automatic t\. . . . . . . 

trai'fic flow security". The U.K. · enfl U.S. have agreed the f'oliowing 

definition of' this term: 

11 lmtomatic traffic flow security is the coroition achieved by 

automatic means, in which an enemy is deniefr knowledge of the volume 

and routing of' traf'fic passed over a·ci~cuit 0 •. 

Thus automatic traffic flow security not o~ly disguises messag~ externals 

but also prevents traffic analyses baaed· ·on t·ot.al volume and message 

lengths._ 

3. Recommendations. 

-~ 

a. The U.K. ana._y.s. fully realise that proper im~lementation of the above 

.. constitutes an ideal, but agree that serious. and. urgent: consideration be given 

to the determination of the maxinrum degree o"f t.ransr:riission security which can be 

.:...__1)l< j \l>' . - . . achieved. \Th~:-;J,cl,~gly recommend that .sm.all W.'.)rking ~oups consisting of 

security advisors arul users shoulr.t be set up on bot_h sides of -che Atlantic to 

~l~~ ~~e 15!o1'lem.- The rosults should be exchangecl between the 

'· U.K. and u.s. and on the basis of these combined pl~s made. __ Although no limit 

should be placed on the ter:ms of reference· ~£' these groups in the field of' 

t~ansmission security, it is felt that the follo"Wine list ~ncludes those items 

on which immediate action is possible: I (1) 

TOI' SE<Mt 

. . 

-· 

. - _\ . }· _j 

.. \;_ 

I' 

•· 
• 

REF ID:A522923 

• TOP-SECRET • 

( 1) New basic call sign book~ shouln be prepared using variroits 

C·:>mpiled in accordance with criteria proviued by NE.ii:.. 

(u.s. e.cti.:.in) 

(2) 1;,greement should Pe reached en the practica?~~ity of using a 

number of call sign encryption key lists in lieu of a 

sinele world wide key. 

(3) $tudy of and recommendations rcgo.rding replacement of the 

current call sign encryption system, b~sed. at least in part 

on the evidence pro(1uced by Exercise M:J\RII'iliR. 

(4-) The following data with re_gar(1 to. authentication should be 

provirlerl: 

( 1) Types of authentication for which systems a.re required .• 

(2) Degree of protection :neede~. 

(3) Chances and scope of plNltterl interrogo-.tion by an enemy_. 

b. The aforementioned working er~ups should consider the remaining 

questions of plain language, plain language headings, frequency changing, 

message ext~rnals in tape relay, together with any other aasoci~ted items as 

rapidly as possible. v5 ..;,~ 

c. N.S.i~. end C.I'.B. should evaluate· methoc1a for providing all 

cryptosystema within a class with identical external charaqt~ristics: Speciel 

attention should be given to a means for e.limina:!:;ing the use of undisguised. 

- <c M 4"'" ~ ~ t.-\ .. i~ the cry-ptosysteni crosen to replace CC.M. 

~ 

system indicators in messages_ pussed, 

3rd Novemper, 1953. 

TOP SECRET 
·' 844 

, . 

. I( 

,., 

.. I. . ·~REF ID:A522~~~ B to the re ort of the 

ity Sub-Committee to the 

Executive Committee. · 

.!JlVus ooMMuNrc.: . .TioNs sEctr.~ITY cm'f.t•'l;CtENcN 19s2• Cor3 • Lf · 

SECURITY SUB-COMMrl'·r:ali: 

REi·ORT ON TR11NSMISSION SECURTI.I 

1. l:'resent Situation •. 

The U.K. and U.S. agree that British and. U.S. measur-es to maintain 

transmission security do not reach the seme standard of efficacy as do those for 

the maintenance of cryptographic security. rrBsent pr~ctices are insuf~icient 

to deny a potential enemy intelligence derived from.the study of elements of 

transmissions external to the cypher text. 

2. Contributory Factors. 

There are a number of inter-related comrnunic~ti"ons ·pre..ctices and methods 

which contribute to this sta~e of insecurity; these are discussed below: 

• 

a. The Use of :ilain Lan.:-.;.ua.ge. 

The use ·of plain language for the transmission of messages, even 

those in themselves unclassified, not only lead.a . tci'-rev.;;la.t:fori ·or 

in~elligence but tends to nullify the good that can be achieved by 

otherwise sound security practices. .Thi~ is.true fort-WO reasons: 

because compilations of individual "unclassified. items" often provide 

intelligence of Secret or even Top Secret classification, and because plain 

language messages, related externally to cypher messages, CE~ jeopardize 

the security of the latt~.::r and of the address procedures employed with 

them. The U.K. ond U.S. agree that radio' transmission of plain laneua.g·e 

messages should be ·forbidden,. regardle.sa of whe1;her classified or not, 

excepting cases covered by the already· agree~·proviso.thQt in tactical 

situations the commanding officer ma;y authorize.the sending of messages . .· . -

by radio in the clear. 

b. The Use of i:lain Langucwe l.O.dresaing on Encrypted Measap;e~ 

The use of plain larigu,age address.in~ on encrypted messages leads to 

·provision of direct intelligence of the order of battle type and also to 

possibilities of assuming 'With .fair accuracy the content of certain of the 

•enoryptea mussages so head(:ld. The U.K, and u.~~. agree that the use of 

plain language a.d.a.ressi~g on classified messages should be abpliahed, 

TOP SECRET 10 ~ 
REF ID:A52292 • 

• TOP SECRET . 

- 2 -

c. Call iigns. 

Call Sign Systems used. by all stations other than the large 

fixed ones which must inevitably be identifiable, must be secure against 

the en~my tracin~ the continuity of id.entity from dey to a.ay. i .. t 

present there is no universal means for providing this call sign security 

although there is agreement on the use of daily changing Dall signs in 

time of war. The U.K. and U.S. have examine~ the basic call sign 

systems and the "call sign encryption plan" and agree the followings 

(1) Daily changing calls should be instituted in time of 

pee.ce. Their value lies not only in the intelligence they 

deny the enemy but in making harder or impossible his task of 

maintaining continuity of identification from peace to war. 

(2) N·ew basic books should be produced and should be compiled 

with properly hatted variants. 

(3) The use of -a common call sign encryption key list for all 

Services world-wide has consiuerable security disadvantages. 

(4) The overall adequacy of the curr~nt system for the encryption .. . 

of call signs should be reinvestigat~a. oz;.d if necessary a new 

one devis~d. i.:ny new system for call sign encryption, in 

a.d~ition to be~ng secure, even with the basic bock 

compromised, must be easy to use and to produce. 

d. Freguency Changing. 

The U.K." and U.S. agree a means· must be found to change 

frequencies at a rapid rate nnd with wide variations; that failure to 

do this will tend to diminish the. security achievable by the other 

praotices under discussion. 

e. External Characteristics of Cryptcsystems. 

The U.K. and. u. s. agree that the fact that cryptosystems can be 

sorted into general types by external characteriat.ics, and into 

specific types by system indicators (discriminants) is a source of 

insecurity tlla.t should be eliminated. /r. ~ ·. . ... 

TOP SECRET 
• · REF ID:A52292. 

--. TOP S~t;RET 

f. .l'..uthentication. 

The U .K. and U.S. agree that the currently approved systems a.nd 

methods for authentication, although secure in many respects, do not in fa.at 

afford a guarantee of the authenticity of transmissions or a positive 

safeguard against intrusion. 

g. ·Message ~xternals in Tape Relay. 

:treaent tape relay systt:ms cannot operate without undisguised 

routing indicators. The U.K. and U.S. ~ree that undisguised routing 

indicators provide value..ble intelligence ruin that th~ir .~ad.io transmission over 

mdic and sensitive line circuits must be eliminated. Therefora, present 

tape relay procedures require a basic overhaul. The u.k. and u.s. agree that 

the most feasible alternative appears to be the adcption af total link 

encryption using orYPtosystems o~a.ble of providing "automatic traffic 

flow security". The U.K. and u.s. have ·a.greed the following definitiGn 

of this term: 

111.:utoma.tio tra.ffio flow security is the condition achieved by 

automatic means, in which an enemy is. denied knowledge of the volume 

and routing of traffic passed over a circuit." 

Thus automatic traffic flow security not only disguises message externals 

but else prevents traffic analyses based on total v~lume and message 

. lengths. 

3. Recommendations. 

a. The U.K. and U.S. fully realise that pr9per implementation of the above 

. ~/JR constitutes a,n ideal, but agree that serious and urgent consirlera.tion ..,, givQ'lf-' 

il 

~the determination of the maximum iiegree .of transm.ission s~.curit;y which can be 

achieved. They accordingly recommend that 1'hie smell W~rkj!18 Groups consisting of 

security advisors end users shoula. be set up on both sides of the .Lclantic to 

provide a solution to the problem. The results should be exchong~d bu-ewe.en the 

U.K. and U.S. and on the basis of these combined plans maiie. Ll though no 

limit should be plnced.on the terms of. reference of these groups in the field of 

transmission security, it is felt that the following list includes those item.3 

on which irrunediate a.ction is possible: -· .. · ... /(1) 

TOP SECRET 
• REF ID:A52292. 

- TOP SECRE'f 

- 4 -

(1) New basic coll.sign books should be prepared using 

variants compiled in a.cc or dance with criteria provided by 

NSJ1 (U.S. action) 

(2) .L·.~_reement should be :r-eached on the practic~ility of using 

a number of call sign encryption key lists in lieu of a 

sin~le 1frorld wide key. 

(3) Study of and recommendl'lticns ree;rrdin~:-replacement of the 

current call sign encryption system, based at least in part 

on the evidence produced by ~xercise MLl:UNJfil.. 

(4) The following data with rege.rd to authentication should be 

-provided: 

(1) Types of authentication for which systems are required. 

(2) Degree of protection neeL1erl. 

(3) Chances and scope of planned interrogaticn. 

b. The aforementioned working gr:::·ups should consider the ·remaining 

questions of pl~.in langu~;e, plain kngua,ee headings, frequency _changing, 

message externals in tape relay, together with any oth~r aasocj.ated ite111s a.a 

rapidly as possible. 

c. N. S. ii. ena. C. i . B. should ev clue met hods for pro vining all 

'•ryptosystems within e. class with ~dentical external characteristics •. .:Jpeci&l 

attention should be given to a means for eliminating ~the use of undisguised 

system indicators in messages· passed in the cryptosystern ch6sen ·to replace CCM .. 

TOP SEGRH 
82 

• REF· ID:A5229~. 

TOP SECRET - -- - , 

~ ~,, .. 

:§; - - _,i.:..:. I -·· 

TO BE HANDLED. IN ACCORDANCE WITH IRSIG . -

f' 

EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

Copy No: 1 

---. __ _ 

/3. 

--- .,_. ----TOP -- ~:: /: .. ____ · ____ ·, -. - SECRET 
REF .ID:A522923 EO 3.3(h)(2) 

PL86-36/50 USC · 605 

-
REF ID:A522923 EO 3.3(h)(2) 

PU. 86-36/50 US: 3605 
---====--~--.. 

REF ID:A522923 EO 3.3(h)(2) 

PL\86-36/50 USC 05 
REF ID:A522923 

- -------

EO 3.3(h)(2) 

PL\86-36/50 USC 3605 
REF ID:A522923 

EO 3.3(h)(2) 

PL 86-36/50 USC 36C 5 

.-
REF ID:A522923 3.3(h)(2) 

86-36/50 USC 3605 
---··------

EO 3.3(h)(2) 

PL\86-36/50 USC 361 ns 

I~--

- - -
~ 

EO 3.3(h)(2) REF PL\86-36/50 USC 

31 05 ID:A522923 
REF ID:A522923 EO 3.3(h)(2) 

PL\.86-36/50 USC 360! 
EO 3.3(h)(2) 

PL\86-36/50 USC 36 5 
-_ -=--=--=-----------

REF ID:A522923 

EO 3.3(h)(2) 

PL 86-36/50 USC 31 05 

.. ::±----

~..\_ •:__,_ _ _____I_ 
REF ID:A522923 

EO 3.3(h)(2) 

PL 86-36/50 USC 3605 
REF ID:A522923 

EO 3.3(h)(2) 

PL 86-36/50 USC 36C 5 
--------- -- - -

REF ID: 

EO 3.3(h)(2) 

PL 86-36/50 USC 36 5 

rt seems•tnnt anaioga of rotor machine::} Will tend to be slower and cosfiier -·- -·-

than analogs of electronic devices. It is extremely diffic"Ult h;:;wever to sa;y 

how much slower and costlil:~r, since operations v?ry w:i.r"!.ely, anrl unexpectetl 
EO 3.3(h)(2) 

PL 86-36/50 USC 3605 

REF ID:A522923 
• 

• .... 

... 

JJ.NNE.X. :B to J,,~pendix c· ' 

LCS(53)/S/Re?ort (Final Draft) 

Expression of Security Requirements 

Considerations Relevant to the Problem 

1. In order to make an assessment the security advisers requi~e to know at 

least:-

a. the degree of confidence to be vlaced in the system 

(the Confidence Factor) 

b. the j_)ro:posed level of use· 

c. the expected traffic load · 

d. the minimuzn acceptab1e message length 

e. (letails of any s~ecial traffic pec-μliarities. 

2. Provision of the inforrnation·required llllder.1b to 1e above presents 

little difficulty but 'letermination of the Confi:lence Factor is not so 

straightforward. The Conficlence ·Fn.ctor m::xy be defined as the tolerable 

expected pro~ortion of unreadable messages to roaln.ble messages within a 

statdu period of time. In. calculating the acceptable Confide?ce Factor it 

will be necessary to.take the following factors into account:-

a. the classification of traffic to be passed in the system 

b. the Intelligence im1>0rtance of the tr<tffic to the enemy 

c. the time factor 

a.. the volume of tr11ffi·c 

e. the echelon of use 

r. the number of holders in a crY'~tonot 

g. the.crypto~eriod 

h. the physical security conrlitions. 

3. In making an assbssraont the security aJvisers will take into account tho 

noI'Illc.'ll incidence of machine failures and operators 1 errors appropriate to the 

echelon and system in question. 

_., .• ... 

·• ... 
.. 

1. 

2, 

' 

3. 

4. 

REF ID:A52292.i&._ 

• ..... •• - ~m~DP~SIRBCeCRHE~IL--• 

TITLE 

ANNEX C to A~pendix C to 

LOS(53)/S/Re ort (Final Draft) 

U, K. CRYPrOGRli.PHIC Rll:QUIREMElNTS PRO-FOR.MA . 

Titla or Codename of equipment 

Equipment to be used by: 

(a) Navy 

(b) Army 

( c) Air Force 

(d) N/,.,TO 

(e) Other 

Level at which equipment is 

be used 

(a) Navy 

(b) Arrey 

( c) J;,ir Force 

(d) N.AT.O 

(e) Misc. 

(a) Ty-.Je of 't'raffi c to be 

passed on the equipment 

( 1) Strategi.c 

(2) Tactical 

(b) Estimated proportion of 

higher classification 

(1) Top Secret 

(2) Secret and below 

to 

. . . 

. ' 

. ... · ... 

.. 

.. • .. .. ·-: 

.. 

. .. . . . 

5. Volume per key 

(a) Desirable maximum 

(b) i-1.cceptable minimum 

6. Number of hol:lers ,. 

i 

I 

I.. 

."!. -
REF ID:A522923 

• ... ·~SECRETt 

7. Message length 

(a) Desirable minimum 

(b) Estimated average 

• 

- 2 -

8. Traffic peculiarities 

(Stereotyped; prc-forma, etc.) 

I 

9. :i:rocea.ure 

(a). Disguiserl indicators 

(1) J~ccepta.ble 

(2) Unacceptable 

(b) B;i.section 

( 1) Acceptable 

(2) Una.Cceptable 

(c) Variable sracing 

(1) Accept.able · . 

(2) Unacceptable 

(d) Continuation prccedure 

( 1) Acc.~ptable 

(2) Unacceptable 

1 O. Category 

(a) Requirement for 

:t.=ublication 

(b) i/L iteplies 

11. Risk of physical ccmp~cmise 

12. 1rype of Orerator 

(a) career 

(b) casual 

13. .i~sc-ciateu staff requiremeI).t 

-· 
84 

REF ID:A52292. 

SECRET. ,.,, 

lil'rnEX C to LCS (53 /_S/R6 (F-inal Draft). 

dated 29th October, 1953. · • 

TITLE 

U .K. CRYPI'OGRAP.HIC RE;-vUIRE1'.lENTS PRO-FORMA 

1·. Title or Cndename of equipment 

2. Equipment t~ be used by: 

(a) Navy 

(b) Army 

( c) Air Force 

(d) NATO 

(e) Other 

Level at which equipment 

be used 

(a) Navy 

(b) Army 

(c) Air Force 

(a) NATO 

(e) Misc. 

is 

4. (a) Type of Traffic to be 

passed on the equipment 

(1) Strategic 

(2) Tactical 

(b) Estimated proportion of 

higher classification 

(1) Top Secret 

(2) Secret and below 

5. Volu~e per key 

(a) Desirable maxim'll!Il 

(b) Acceptable minimum 

6. Number of holders 

to 

/7 .. 
,• 84 REF ID:A522923 

SECRET. 

- 2 -

·7. Message length 

(a) Desirable minimum 

(b) Estimated average 

B. Traffic peculiarities 

(Stereotyped; pro-forma, etc. ) 

9. Procedure 

(a) Disguised indicators 

( 1 ) Acceptable 

(2) Unacceptable 

(b) Bisection 

( 1) Accep'il1ble 

(2) Unacceptable 

(c) Variable spacing 

( 1 ) Acceptable 

(2) Unacceptable 

(d) Continuation procedure, 

(a) Acceptable 

(b) Unacceptable 

10. Category 

(a) Requirement for 

Publication 

(b) P/L Replies 

11. Risk: of physical compromise 

12. Type of Operator 

(a) career 

(b) casual 

13. I Associated staff requirement 

•