The Registration Room

A complete example

Introduction

At BP, Hut 6 is responsible for breaking the Army and Air Force keys. It is made up of several sections called “Room”. It is the Registration Room (RR) which receives the messages from the Y Stations and the metadata related to these interceptions.

One of the first tasks of the RR is to create the Blists (Bannister Lists) which reference the messages in relation to their membership in a particular Enigma network. To do this, the RR uses metadata: frequencies, call-signs, the geographical location of the stations. This geographical location can be deduced from the calls-signs of the stations, from their connection with other stations, from the traffic volume, from the identification of radio operators and also from the direction finding (D/F).

Another element which makes it possible to reconstitute the Enigma networks (which do not necessarily correspond exactly to a radio network) are the kenngruppen. Each Enigma network was identified by German operators by a trigram present at the end of the first group of the message. It was chosen by the sender from a list of 4 or 5 kengruppen present on the list of keys.

The Blist

On each entry of a Blist, there is essential information about each message and of course a reference that allows you to find the complete message.

Blists and messages are transmitted to the Crib Room and also (after breaking the key) to the Decipher Room (DR).

On the Blist, each message is referenced by a line. The following fields are present:

• Station Y and the intercept order number.
• Call-signs (sender / recipient),
• The frequency,
• The number of letters of the cryptogram,
• The grundstellung, the indicator (the message key encrypted at the position of the grundstellung),
• The 1st group of the cryptogram which contains the kengruppe.

An example

1) Here are the messages sent by a Station Y and received by teleprinter

ZER/1. 6QG APY 1475 Kcs 1200 31 =ROM= =LNS= 
QKNVT WCGLV EUTCF ZTQSA WJCSR FQOOZ Z

ZER/2. APY N7Y 1475 Kcs 1630 245 =BER= =VEU=
FVNVT HWHVO VRWGM UBOPE PNOME PJNST CTAMT FGFGC ZDBGD XLUDH 
UADKC AWYXJ TGIXI ZAWRX DYCXR JKXAW EQPXN IVZXS YQMWK QSVPB 
UKMEP GKGHL BNZBC CVBQZ AWJFE ZQKWT HSDGZ LQDJD XYQCJ UTBTE 
EOJBT ZRLIU LTKXA AWTYT KVYHO SEKWU ZHYSO QOEFN TLISM VMAJS 
OYYXE CPGNJ QJGGJ YDBPP HTFZO ZTXML MCSEC ZSZPX NIKDQ

ZER/3. SAD NT3  950 Kcs 1635 245 =BLU= =DAP=
GRAVR KWTJX USVXU TLKXG EGWGG NIIVC TITJM IIQNM UEAFT HCXHK 
ZXRYW ZERLT IBTMT OHEND QIWWH XVOCV EUWNJ EVIZB VJOOC ETRCJ 
LRLYB JZLZE GPXTI YCOWK ABGZS FXGQV XWULR PHQYM ODVZX NDLBG 
OGNWQ QQMAX OWMZS PYSBJ KGGZW QIUEA CBXUD PMSCY IYWMT BBNQI 
EQZRO IADEG QERQW QTPWY BOVNZ SMWAF MWLFR AILXV QNZGK

ZER/4. 9HD SAD 950 Kcs 1715 2TLE=1TL= 198 =TRI= =BBG=
KJTBX ABXPX DRKHA UMTTU OFCMD VPUZK BKNKB DKVMI MQSMI DFHUA 
QXXOW VJQEV TNNWO TYRLV MDHPM JFWWG VPFZI EFCFO GIFQL PNVRA 
CPIDX JJROR EKPLX CHHVI BGYFY DGUFU YQKTG YHYNO LWQWX HPMBK 
JQIGT YDQQE PXKPP MHURX FJGCX VHQKM DLGOR CGGUX EBSDU ZES

ZER/5. 9HD SAD 950 Kcs 1720 2TL= 133 =AFR= =RRG= 
NTVRA TQRLD YUCUB PWVCH GXKHX RXFUT SDHCW ABBJM TOQZN JUYYJ 
MQXQH QJPCW PSSJP OCTWJ OCCNK JSCGE QZQCY XTTSU TFOIM DTWAO 
FAOWJ RBMVK JWPDI QYDGY EMJAJ CGBYL NKL

2) Reconstruction of Enigma networks

a - Red Key

Berlin                     SAD	
Tripoli                    9HD
Alle (broadcast)           TN3
Kenngruppen: mek ayn udm nvt

b - Light Blue key

3) Blist for each Enigma network

a - Red Key

ZER/1. 6QG APY 1475 Kcs 1200 31 =ROM= =LNS= QKNVT 
ZER/2. APY N7Y 1475 Kcs 1630 245 =BER= =VEU= FVNVT

b - Light Blue Key

ZER/3. SAD NT3 950 Kcs 1635 245 =BLU= =DAP= GRAVR
ZER/4. 9HD SAD 950 Kcs 1715 2TLE=1TL= 198 =TRI= =BBG= KJTBX
ZER/5. 9HD SAD 950 Kcs 1720 2TL= 133 =AFR= =RRG= NTVRA