Enigma procedure (1931)

Introduction

A document (DECKBLATT zur SCHLÜSSELLANLEITUNG für die CHIFFRIERMASCHINE "ENIGMA"), published at the latest in late 1931 corrects the original Enigma procedures (1930). This document does not replace previous manuals. It actually contains the list of corrections to be made in the manuals.

In short, this document introduces for each daily key a network identifier, the Kennzeichnung.

The Kennzeichnung

Although in the previous document it is indicated that a key had a limited scope (a Division, …) one can imagine that in fact only one key existed. Indeed no technique for discriminating an encryption network is described. In addition, the key table example does not include any discriminant.

The “Deckblatt” corrects this situation. A key table now must include an additional column (Kennzeichnung) which allows identification of the network.

An example of key list

 Geheim!  Heeres Maschinen Schlüssel - Monat Juli 1931
      II III I  (Walzenlage)
Tag Ringstellung Grundstellung Steckerverbindungen            Kennzeichnung
 31   23  9 14     15 22  5    14/19  6/23  2/13  9/11 16/26  7/22  130-540
 30   12 15  9      6 21 23     4/17 10/21 23/26  5/22 18/19  2/16  450-850
 29   14 18 15     20 23 25     5/20 11/17  3/4  10/26  2/12 16/22  160-630
 28   26 24 25     10  6  4     7/12  2/24 13/19 18/21  4/15 14/25  300-770
 27   16 18  2      2  1 15    12/14  4/26  6/8  16/22 19/20 17/18  150-590
 26   18  3 23     11  5 10     8/26  6/25  9/14  4/21 10/12 18/24  380-790

An example of encryption

The procedure is almost identical to that of 1930. The only difference is that the random three-digit number at the end of the header is replaced by the Kennzeichung taken from the key of the day and which identifies the encryption network.

Here is a sample message (dated July 30). It's up to you to decipher it.

1730 - 148 - 494
PKDBM MPWPC SHZXM ZKLJP MJSGV VEXNW JFJHD DVIPR IHPFH DPAFH
RMMLE RMZEP ROFZO CNJYH EPYHP UATLC QHLGG LDUHG VRCUA NTDIE
EQSZX IPTHH ZDKVI FZQTF QCLQQ XNEJA QMNBS DUY