Editing Fish (cryptography) (section)

== History ==
In June 1941, the British [[Y-stations|"Y" wireless intercept stations]], as well as receiving [[Enigma machine|Enigma]][[cipher|-enciphered]] [[Morse code]] traffic, started to receive non-Morse traffic which was initially called NoMo.<ref>{{ Harvnb | Copeland | 2006 | p = 338 }}</ref> 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 Communications Headquarters#Government Code and Cypher School|Government Code and Cypher School]] at [[Bletchley Park]], revealed that the Germans called the wireless teleprinter transmission systems ''"Sägefisch"'' (sawfish). This led the British to use the code '''''Fish''''' dubbing the machine and its traffic '''''Tunny'''''.<ref>{{Cite book |last1=Hinsley |first1=Francis Harry |url=https://books.google.com/books?id=j1MC2d2LPAcC&q=Introduction+to+fish, |title=Codebreakers: The Inside Story of Bletchley Park |last2=Stripp |first2=Alan |date=2001 |publisher=Oxford University Press| pages = 141–148 |isbn=978-0-19-280132-6 |language=en}}</ref>

The enciphering/deciphering equipment was called a ''Geheimschreiber'' (secret writer) which, like Enigma, used a [[involution (mathematics)|symmetrical]] [[substitution alphabet]]. The teleprinter code used was the [[Baudot code#ITA2|International Telegraph Alphabet No. 2 (ITA2)]]—Murray's modification of the 5-bit Baudot code.

When the Germans invaded Russia, during World War II, the Germans began to use a new type of enciphered transmission between central headquarters and headquarters in the field. The transmissions were known as Fish at Bletchley Park. (See [[Lorenz cipher]], [[Cryptanalysis of the Lorenz cipher]].) The German army used Fish for communications between the highest authorities in Berlin and the high-ranking officials of the German Army in the field. 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. However, these transmissions were so challenging to decrypt that even with the assistance of the high speed [[Colossus computer]], the messages could not be read until several days later.<ref>F.H. Hinsley and Alan Stripp (eds.) ''Code Breakers: The Inside Story of Bletchley Park'', Oxford University Press, 1993.</ref> “Vital intelligence was obtained about Hitler’s intentions in the run up to D-Day 1944.”<ref>{{cite web|url=http://www-gap.dcs.st-and.ac.uk/~history/Obits/Tutte.html|work=The Times|title=Professor Bill Tutte: Mathematician who, as a Bletchley Park codebreaker, gained access to the ciphers of the German Army High Command|access-date=21 May 2013|archive-url=https://web.archive.org/web/20160304192821/http://www-gap.dcs.st-and.ac.uk/~history/Obits/Tutte.html|archive-date=4 March 2016|url-status=dead}}</ref>