The Flossenbürg Messages

  KZ Flossenbürg


  KL Flossenbürg

Photo: KZ-Gedenkstätte-Flossenbürg © 2005

During an ongoing project of decoding 60 year old German Army Enigma ciphers we have come across a large number of enciphered radio messages from and to the concentration camp Flossenbürg. The messages, 258 in total, are enciphered on the Wehrmacht Enigma machine using a special concentration camp key, KL-Maschinenschlüssel. The messages are in two batches, the Blue and Red series, corresponding to outgoing and incoming messages respectively.

We have developed a new method of breaking Enigma enciphered messages. The method is using statistical techniques and the hill climbing search algorithm to recover the Enigma key. The cryptanalytical method is of the type described as ‘ciphertext only’ attack and contrary to methods used at Bletchley Park during the Second World War, does not rely upon probable words, cribs. The technique allows attacking messages as short as 100 letters long; the shortest message broken to date is 78 letter long.

An article describing the technical details on how we have attacked and broken these old messages has recently been submitted to Cryptologia, a quarterly journal specializing in cryptology. We have prepared a few selected pages from this forthcoming article which we make available here in PDF format. This will make clearer the scope and complexity of this project.

Some of these messages are of historical interest and will be published here. The PDF message files contain full ciphertext and Enigma keys for those who are interested in the cryptographical aspects of this work. The complete collection of messages will probably be made available in some form at a later date.




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The material described on these pages is created, collected, edited and published
by Geoff Sullivan & Frode Weierud, © April 2005

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