FISH (cryptography)

The FISH stream cipher is a fast software based stream cipher using Lagged Fibonacci generators, plus a concept from the shrinking generator cipher. The name is an acronym for "Fibonacci Shrinking". It was published by Siemens in 1993.

FISH is quite fast in software and has a huge key length. However, in the same paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few thousand bits of known plaintext.

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FISH was also the British code-name for German teleprinter ciphers used during World War II, including the Lorenz Schlusselzusatz ("Tunny") and the Geheimfernschreiber ("STURGEON"). Ironically, the STURGEON Fish cipher was also produced by Siemens, and was broken by (among others) mathematicians who trained at the same university as Professor Anderson.

See also: Bletchley Park, Colossus computer.