Fish (cryptography)

For the (FIbonacci SHrinking) stream cipher published in 1993, see FISH (cipher).

Fish (sometimes FISH) was the Allied codename for any of several German teleprinter stream ciphers used during World War II. While a large number of links were monitored, at least three different encryption systems were distinguished:

• Tunny — the Lorenz SZ 40/42 from Lorenz Electric. Tunny traffic was read successfully at Bletchley Park, using the famous Colossus computer.
• Sturgeon — the Siemens and Halske T52 from Siemens. Although Bletchley Park managed to work out Sturgeon, they never read much of its traffic.
• Thrasher — the machine that generated this traffic does not appear to have been identified.

See also: Ultra

References

• W. Mache, Geheimschreiber (Cryptology: Yesterday, Today and Tomorrow, Artech House, Norwood, 1987)
• C. Deavours and L. Kruh, Mechanics of the German Telecipher Machine (also reprinted in Cryptology: Yesterday, Today and Tomorrow)