Enigma procedure (1943)

Abandonment of the kenngruppe

At the end of 1943, an important change occurred in the Enigma procedures: the abandonment of discriminants (the kenngruppen). This change took place on September 1 for the army and on November 1 for the air force.

How could an operator choose the encryption key? I suppose it was based on call-signs (a similar change took place among the Americans with the M-209 in the following months). Each unit belonging to the same Enigma network was identified by its radio call sign. If the unit belonged to more than one Enigma network, it was identified by more than one call sign.

There is no document to say whether this procedural change corresponded to the edition of a new manual or to the correction of the 1940 manual.

This change greatly complicated the work of Hut 6 in BP. The new procedure slows down the processing of messages enormously. To cope with this, Hut 6 had to increase the staff of the Registration Room (RR) from 220 to 300 people. Likewise the Y stations had to give more information to the RR to help them discern the different networks.

Example

Call Sign

                            
Luftgau I	Königsber: GS6,     Bubenrod:   7BV
Luftgau IX	Weimar:    WMR,     Ebsdorf:    9TH

Key-Tables

Geheim - Maschinenschlüssel für Monat Dez.r 1943 - N°876
      Luftwaffe - Luftgau I
Tag Walzenlage     Ring.      Steckerverbindungen
 31 I    III  II   16 21 10 AM HU DY EG PS BN KT FJ OZ QX
 30 IV   II   V     9 15 22 HN TW EI GX LV JM DU OQ FP CZ
 29 V    IV   II    2 12 14 IN ET CS AU BX GV JR DQ FY MO
 28 II   V    I    20 25 13 AG KU OS FR EL IP CW BT HY MV
 27 V    I    II   20 21 24 DY EJ OZ FW SU BI HK MT AV CL
 26 II   I    V     1  3  4 JO AP VX QT LR IN GZ SW EK FU
 25 I    V    IV   10 12  3 GM AH LP DX SU FR CN EZ JO IV

Geheim - Maschinenschlüssel für Monat Dez.r 1943 - N°245
      Luftwaffe - Luftgau IX
Tag Walzenlage     Ring.      Steckerverbindungen
 31 IV   II   V    10 17 16 EJ CY NW FL KM AG PU RZ DO QT
 30 IV   I    III   9 14  2 SZ OQ FT CI GK MX PY RW LV EH
 29 I    II   V    22 19 25 GX FS OT IV KZ DU BH AM JP QY
 28 I    IV   II    1 12 18 CP TV AY ES HJ BQ UW FZ KM OX
 27 III  II   V    10 26  6 TZ JN PV KW DQ IM BO AS RY FL
 26 II   V    III  16 17 23 PX CT VZ BW AU HK DQ OS GR JM
 25 I    V    III  26  3  7 EK GL DM AJ QY BH WZ FP OT IV

Crytogram

Try to decipher the following message received on December 25:

WMR  9TH  - 1120 – 75   =WEI=  =BJH=
WSLEK KYKZX LJUEL RSCWE OQOVW GHVRM OKQYV DLEGU SAYNF GEGNH
IWXWX PYZSC CGTWZ UUYMK MFZSD