Card catalog (cryptology)

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The card catalog, or "catalog of characteristics," in cryptography, was a system designed by Polish Cipher Bureau mathematician-cryptologist Marian Rejewski, and first completed about 1935 or 1936, to facilitate decrypting German Enigma ciphers.[1]

History[edit]

Preparation of the card catalog, using the cyclometer that Rejewski had invented about 1934 or 1935, was a laborious task that took over a year's time. But once the catalog was complete, obtaining Enigma daily keys was a matter of some fifteen minutes.[2] [3]

When the Germans changed the Enigma machine's "reflector," or "reversing drum," on November 1, 1937, the Cipher Bureau was forced to start over again and produce a new card catalog, "a task," writes Rejewski, "which consumed, on account of our greater experience, probably somewhat less than a year's time."[2] On September 15, 1938, the Germans changed entirely the procedure for enciphering message keys, and as a result the card-catalog method became completely useless. This spurred the invention of Rejewski's cryptologic bomb and Henryk Zygalski's "perforated sheets."[4]

Notes[edit]

  1. ^ Marian Rejewski, "The Mathematical Solution of the Enigma Cipher," pp. 284–87.
  2. ^ a b Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", p. 242.
  3. ^ Marian Rejewski, "How the Polish Mathematicians Broke Enigma," p. 264.
  4. ^ Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", pp. 242–43.

References[edit]