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.[1][2][3] Enciphered teleprinter traffic was used between German High Command and Army Group commanders in the field, so its intelligence value (Ultra) was of the highest strategic value to the Allies.[4] This traffic normally passed over landlines, but as German forces extended their reach out of western Europe, they had to resort to wireless transmission.[5]

Contents

History

In June 1941, the "Y" wireless intercept stations, as well as receiving Enigma-enciphered Morse code traffic, started to receive non-Morse traffic which was initially called NoMo.[6] NoMo1 was a German army link between Berlin and Athens, and NoMo2 a temporary air force link between Berlin and Königsberg. 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), so the name "Fish" was adopted for this traffic.[7] The enciphering/deciphering equipment was called a Geheimschreiber (secret writer) which, like Enigma, used a symmetrical substitution alphabet. The teleprinter code used was the International Telegraph Alphabet No. 2 (ITA2)—Murray's modification of the 5-bit Baudot code. The NoMo1 link was initially named Tunny, a name which later went on to be used both for the Lorenz SZ40/42 Geheimschreiber machines, and also for the Bletchley Park analogues of them. The NoMo1 link was subsequently re-named Codfish.[8]

A large number of links were monitored by the Y-station at Knockholt and given names of fish. These included Bream (Berlin-Rome), Herring (Rome-Tunis), Jellyfish (Berlin-Paris), Grilse (Berlin-La Roche), Mullet (Berlin-Oslo), Turbot (Berlin-Copenhagen), Dace (Berlin-Königsberg), Whiting (Königsberg-Riga), Perch (Königsberg-Central Belarusse), Squid (Königsberg-N Ukraine), Octopus (Königsberg-E Ukraine), Stickleback (Königsberg-S Ukraine), Smelt (E Ukraine-S Ukraine), Grayling (Königsberg-Belgrade), Tarpon (Berlin-Bucharest), Gurnard (Berlin-Belgrade), Chubb (Belgrade-Salonica), Flounder (Salonika-Rhodes) and Codfish (Berlin-Salonika).[9]

Traffic Code names

Sturgeon was the name given to traffic encoded with the Siemens and Halske T52 Geheimschreiber.[10][11] 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.[12] 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.

Thrasher was the name used for traffic enciphered on a Geheimschreiber that was probably the Siemens T43 one-time tape machine. This was used only on a few circuits, in the later stages of the war and was diagnosed at Bletchley Park, but considered to be unbreakable.

List of senior involved staff at Bletchley Park

Including both executives and cryptographers on FISH (Tunny) in the Testery.

See also

Notes

  1. ^ Mache 1986, pp. 230–242
  2. ^ Deavours & Kruh, pp. 243–247
  3. ^ Mache 1989, pp. 97–117
  4. ^ Copeland 2006, p. 47
  5. ^ Lewin 2001, p. 130
  6. ^ Copeland 2006, p. 338
  7. ^ Gannon 2006, p. 102
  8. ^ Gannon 2006, p. 170
  9. ^ Copeland 2006, p. 41
  10. ^ Weierud 2006, pp. 307–327
  11. ^ Smith 2006, p. 35
  12. ^ McKay 2006, pp. 328–333

References

 
Cipher machines
Rotor machines:
Mechanical:
Teleprinter:
Secure voice:
Miscellaneous: