Fish (cryptography)

Fish (or FISH) was a code name for a series of Allied stromchiffrierter encryption systems of the German Wehrmacht, which were based on telegraph technology.

When listening to a large number of messages at least three different systems could be identified:

• Tunny - the key machine SZ 40/42 of the C. Lorenz AG. The news of this device could be decrypted at Bletchley Park with the help of the Colossus.
• Sturgeon - the T52 Siemens & Halske. Although Bletchley Park was able to decipher this code, never many messages were processed.
• Thrasher - the machine that encrypted this message was never positively identified. Maybe it was the Siemens & Halske T43 -Telegraph.