Kiss (cryptology)

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As Kiss ( English for: "Kuss"), occasionally also as RE (from re-encipherment for "re- encryption "), the finding of two or more ciphertexts is called in cryptology , which the decipherer assumes that they are come from the same plaintext . This case, in which a plaintext has been encrypted several times in different ways, and that the corresponding ciphertexts can be compared with one another, is also referred to as “ciphertext-ciphertext compromise” (or somewhat shorter as “ciphertext-ciphertext compromise”).

application

Evidence for the assumption of this case can be that the compared ciphertexts have the same length, that the texts were sent at about the same point in time, and that, possibly in the case of a radio transmission, the call signs of the radio messages indicate this.

The term kiss was mainly used by the British " code breakers " in Bletchley Park , England , who wanted to describe this sweet moment of happiness of finding two secret texts of the same origin, which for a cryptanalyst can be compared to a real kiss . Friedrich L. Bauer comments on this choice of term: "There could not have been a better way of expressing the decipherers' delight over such a stroke of luck."

A kiss basically represents an ideal " crib " (German: probable word), but it is much more than just a "probable word" that the code breaker assumes that it occurs in encrypted form in ciphertext. In the case of a kiss , the complete text can actually be assumed to be known.

In particular, a kiss can be used to break into a hitherto unbroken encryption system . An example of this is the four-cylinder Enigma M4 used by the German submarines in World War II . Warning messages, for example of drifting mines, were not infrequently passed verbatim by the German navy to surface ships that did not have the Enigma machine and to the submarines. Since the British were able to break the shipyard key (a bigram encryption ) used for the surface ships relatively easily, they knew the literal content of the corresponding submarine radio messages and were able to use this knowledge to break into the M4 system and then further, to decipher significantly more important submarine radio messages . Occasionally the British even deliberately provoked incidents of this kind, only to receive the German radio messages with known content that were to be expected promptly and called this technique “ gardening ” ( literally in German : “gardening” ).  

See also

literature

Web links

  • Christine Large: Some Human Factors in Codebreaking . (English) PDF; 0.3 MB.Retrieved March 22, 2010.
  • Tony Sale: The Bletchley Park 1944 Cryptographic Dictionary . (English) Publication, Bletchley Park, 2001. Accessed: March 22, 2010. PDF; 0.4 MB

Individual evidence

  1. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, p. 399ff.
  2. ↑ Tony Sale: The Bletchley Park 1944 Cryptographic Dictionary. Publication, Bletchley Park, 2001, p. 22. Accessed: March 22, 2010. PDF; 0.4 MB
  3. ↑ Gordon Welchman: The Hut Six Story. Breaking the Enigma Codes. 2000, p. 163.
  4. ↑ a b Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, p. 400.
  5. ↑ Michael Smith: ENIGMA decrypted. The "Codebreakers" from Bletchley Park. Heyne, Munich 2000, ISBN 3-453-17285-X , p. 88.