One catalog

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The one-Catalog (English: "One catalog" ) was a special kryptanalytisches resource that during the early days of World War II by British cryptanalysts to the deciphering of the German Navy used cipher machine Enigma M3 was used. It was created using a special machine called a "baby" .

history

U-boats like the German U 505 threatened the British supply lines

At the beginning of 1940, the British code breakers in Bletchley Park (BP) in England , about 70 km north-west of London , still had no effective electromechanical decoding machines (see also: Turing bomb ) and were dependent on manual decoding methods. Of particular importance to the British war effort was the securing of the sea routes for their merchant ships against the growing German submarine danger . A break in the secret radio traffic encrypted by the German Navy with the help of the Enigma-M3 was essential.

Unlike the of the German Luftwaffe with the Enigma I encrypted messages that continuously by the British already in January 1940 and almost the entire Second World War broke could be, the encryption method of the German Navy proved stubborn. This was not only due to the fact that they used the cryptographically stronger Enigma M3 with three out of eight reels (instead of just five as in the Enigma I), but above all because of a particularly sophisticated spell key agreement that the British cryptanalysts found difficult to overcome.

generation

Enigma radio message intercepted in Bletchley Park (Part two of a three-part message)

As soon as a single marine radio message could be deciphered, three of four key elements for all other radio messages of the same key network were uncovered within a two-day period, namely roller position , ring position and plug . Only the roller position , i.e. the manually adjustable starting position of the three rollers, which was selected individually and differently for each saying, was unknown. There are 26 options (A to Z) for setting the rollers for each of the three rollers. A total of 26³ = 17,576 different roll start positions are possible.

In order to find the right one as quickly and easily as possible (without machine help), the British code breakers decided to create a table listing all 17,576 cases. You had noticed that one of the most frequent words in German naval radio messages was the number word " Eins ". This resulted from the fact that the Enigma can only encode the 26 capital letters and no digits . For example, time, quantity and coordinate information, which often contain the number one, had to be written out by the Germans as EINS and then encrypted. The British take advantage of this weakness by systematically encrypting the tetragram ONE with the help of a special machine called "The Baby" with all possible 17,576 roller start positions, with known roller positions, ring positions and plugs. You received a tetragram, for example LTLW or NYUG, for all roller start positions from AAA to ZZZ. Then they sorted the total of 17,576 received tetragrams in alphabetical order. This resulted in the one catalog , i.e. a list with 17,576 alphabetically sorted tetragrams and the associated roller start positions.

application

The British mostly used their own TypeX key machine for the mechanical decryption of the broken radio messages

Then the still unbroken German radio messages were viewed and the corresponding tetragram of the ciphertext read off at the points where the encryption of the word Eins was suspected as " Crib " and looked up in the Eins catalog. If it did not appear there, it was to be concluded that the crib was incorrect and that at that point in the text it had not been encoded as ONE. However, if the ciphertext tetragram was in the one catalog, the corresponding cylinder position on the right was taken from it.

The roller position read off in the one catalog was now set on a key machine that was already correctly preset according to the known roller position, ring positions and plug. For this purpose "Hut 8" (German: Baracke 8), the organizational unit of BP specializing in the deciphering of German naval communications, used mostly not one of the few captured German Enigma machines, but specially adapted British key machines " TypeX " were used.

If the ciphertext tetragram was entered via the machine's keyboard, the word ONE naturally appeared as the text. The decisive factor was which letters followed when one tried to decipher the secret letters following the crib . If it was a confused sequence of letters, similar to a random text , then obviously you had landed a miss and the crib was wrong. However, if you received German plain text, you had found the right place and could then decipher the entire radio message.

In this way, BP not only succeeded in breaking individual radio messages, but it was also possible to penetrate deeper and deeper into the German spell key procedure and gradually to completely reconstruct the crucial "double-letter exchange tables" used .

literature

  • Kris Gaj, Arkadiusz Orłowski: Facts and myths of Enigma: breaking stereotypes. Eurocrypt, 2003, p. 121ff. Accessed: February 13, 2012. PDF; 0.1 MB
  • Francis Harry Hinsley , Alan Stripp: Codebreakers - The inside story of Bletchley Park . Oxford University Press, Reading, Berkshire 1993. ISBN 0-19-280132-5
  • Tony Sale : The Bletchley Park 1944 Cryptographic Dictionary . Publication, Bletchley Park, 2001, p. 34. Retrieved February 13, 2012. PDF; 0.4 MB
  • Hugh Sebag-Montefiore : Enigma - The battle for the code . Cassell Military Paperbacks, London 2004, ISBN 0-304-36662-5
  • Michael Smith: Enigma deciphered - The "Codebreakers" from Bletchley Park . Heyne, 2000. ISBN 3-453-17285-X

Individual evidence

  1. ↑ Tony Sale: The Bletchley Park 1944 Cryptographic Dictionary . Publication, Bletchley Park, 2001, p. 34. Retrieved February 13, 2012. PDF; 0.4 MB
  2. ^ Joan Murray : Hut 8 and naval Enigma in Francis Harry Hinsley, Alan Stripp: Codebreakers - The inside story of Bletchley Park . Oxford University Press, Reading, Berkshire 1993, p. 114. ISBN 0-19-280132-5
  3. ^ Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 11. ISBN 0-947712-34-8
  4. ^ Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 230. ISBN 0-947712-34-8
  5. ^ Hugh Sebag-Montefiore: Enigma - The battle for the code . Cassell Military Paperbacks, London 2004, p. 393. ISBN 0-304-36662-5
  6. ↑ Friedrich L. Bauer : Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, ISBN 3-540-67931-6 , p. 143.
  7. ^ Hugh Sebag-Montefiore: Enigma - The battle for the code . Cassell Military Paperbacks, London 2004, p. 136. ISBN 0-304-36662-5