Fish (cryptography)

The parallel Enigma-enciphered link to NoMo2, which was being read by Government Code and Cypher School at Bletchley Park, revealed that the Germans called the wireless teleprinter transmission systems "Sägefisch" (sawfish).

The Fish traffic which the personnel at Bletchley Park intercepted, contained discussions, orders, situation reports and many more details about the intentions of the German Army.

The Tunny links were based on two central transmitting and receiving points in Strausberg near Berlin for Army generals in the West and one in Königsberg in Prussia for the Eastern Front.

[12][13] Cryptanalysis of the Lorenz cipher at Bletchley Park was assisted initially by a machine called Heath Robinson and later by the Colossus computers yielded a great deal of valuable high-level intelligence.

Walter Jacobs, a US Army codebreaker who worked at Bletchley Park, wrote in an official report on the operation to break Tunny that in March 1945 alone 'upward of five million letters of current transmission, containing intelligence of the highest order, were deciphered'.

[16][17] In May 1940, after the German invasion of Norway, the Swedish mathematician and cryptographer Arne Beurling used traffic intercepted from telegraph lines that passed through Sweden to break this cipher.

[18] Although Bletchley Park eventually diagnosed and broke Sturgeon, the relatively low value of the intelligence gained, compared to the effort involved, meant that they did not read much of its traffic.