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← Codebooks
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Bigram tables
Doppelbuchstabentauschtafeln fur Kenngruppen - wanted item

During WWII, the German Kriegsmarine (Navy) used a variety of codebooks in combination with the Enigma M3 and later the Enigma M4 machine. The German Naval message procedures were extremely complex and caused the code breakers at Bletchley Park many headaches, especially after the introduction of the M4. Below is an example of a real German naval bigram table.

When encrypting a naval message on the Enigma cipher machine, the message was first converted into a much shorter one, using a series of so-called short message books. The operator then had to pick a message key for its encryption, as described in the Naval Procedure of 1940 [B].

This involved the use of a wide variety of code material, including Schlüsseltafel M Allgemein, Zuteilungsliste, Tauschtafelplan, Kenn­gruppen­buch and the Doppelbuchstabentauschtafeln (bigram table) shown here. More information about this procedure on our Enigma M4 page.
  

The codebooks of the U-Boot department of the German Kriegsmarine were printed with red water-solvable ink on pale red paper. They could be wiped simply by throwing them into the water. A warning to this effect is printed on top of the page that is shown in the image above:

Vorsicht! Wasserlöslicher Druck!

which means: Careful! Water solvable print!. The slightest trace of water immediately caused the ink to start bleeding. When left behind in a sinking U-Boot, the codebooks would wipe themselves automatically, which is why it was so hard to capture them during World War II.

The bigram tables and associated documents shown here, are from the collection of Arthur Bauer [1]. Many thanks for allowing us to make some photographs and high-resolution scans of it [A]. The exact keying procedure that was used by the German Kriegsmarine is described in great detail by Belgian historian Dirk Rijmenants on his website [2].

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 Download the scanned pages
Documentation
  1. Doppelbuchstabentauschtafeln für Kenngruppen
    Bigram substitution table for Message Indicators. Crypto Museum #300356. 1

  2. Oberkommando der Kriegsmarine, Der Schlüssel M, Verfahren M Allgemein
    Operating procedure for Naval Enigma. Berlin 1940.
    Crypto Museum #300359. 1
  1. Documents kindly supplied by Arthur Bauer [1].

References
  1. Arthur Bauer, Foundation for German communication and related technologies
    Museum for historical German technology (mainly used before and during WWII).

  2. Dirk Rijmenants, Enigma Message Procedures
    Acurate descriptions of the Wehrmacht and Kriegsmarine Enigma procedures.
Further information
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Crypto Museum. Created: Friday 19 September 2008. Last changed: Saturday, 08 July 2017 - 09:26 CET.
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