View source for Fish (cryptography)

{{For|the stream cipher published in 1993|FISH (cipher)}}
{{Use dmy dates|date=October 2019}}

[[File:Russian Fish.jpg|thumb|German prisoners prepare the "Russian Fish" for loading and shipment to England.<ref>{{cite book|title = The Ultra Americans: The U.S. Role in Breaking the Nazi Codes: Thomas Parrish: 9780812830729: Amazon.com: Books|isbn = 978-0812830729|last1 = Parrish|first1 = Thomas D.|year = 1986| publisher=Stein and Day |url-access = registration|url = https://archive.org/details/ultraamericansth00parr}}</ref>]]
'''Fish''' (sometimes capitalised as '''FISH''') was the UK's GC&CS [[Bletchley Park]] codename for any of several German [[teleprinter]] [[stream cipher]]s used during [[World War II]].<ref>{{ Harvnb | Mache | 1986 | pp = 230–242 }}</ref><ref>{{ Harvnb | Deavours | Kruh | 1986 | pp = 243–247 }}</ref><ref>{{ Harvnb | Mache | 1989 | pp = 97–117 }}</ref>  Enciphered teleprinter traffic was used between [[Oberkommando der Wehrmacht|German High Command]] and [[List of German army groups in World War II|Army Group]] commanders in the field, so its intelligence value ([[Ultra (cryptography)|Ultra]]) was of the highest strategic value to the Allies.<ref>{{ Harvnb | Copeland | 2006 | p = 47 }}</ref> This traffic normally passed over landlines, but as German forces extended their geographic reach beyond western Europe, they had to resort to wireless transmission.<ref>{{ Harvnb | Lewin | 2001 | p = 130 }}</ref>

Bletchley Park decrypts of messages enciphered with the [[Enigma machine]]s revealed that the Germans called one of their wireless teleprinter transmission systems "{{lang|de|Sägefisch}}" ('[[sawfish]]') which led British [[cryptographer]]s to refer to encrypted German [[Wireless telegraphy|radiotelegraphic]] traffic as "Fish." The code "Tunny" ('[[tunafish|tuna]]') was the name given to the first non-Morse link, and it was subsequently used for the Lorenz SZ machines and the traffic enciphered by them.

== 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>

== Traffic code names ==
===Tunny===
[[File:Lorenz-SZ42-2.jpg|right|280px|thumbnail|The Lorenz SZ42 machine with its covers removed. [[Bletchley Park]] museum]]
The NoMo1 link was initially named '''Tunny''' (for tunafish), a name which went on to be used both for the [[Lorenz SZ 40|Lorenz SZ40/42]] machines and for the Bletchley Park analogues of them. The NoMo1 link was subsequently renamed Codfish.<ref>{{Harvnb|Gannon|2006|p=170}}</ref> A large number of Tunny links were monitored by the [[Y-stations|Y-station]] at [[Knockholt]] and given names of fish. Most of these were between the ''[[Oberkommando der Wehrmacht]]'' (German High Command, OKW) in Berlin and German army commands throughout occupied Europe. 

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. The number of radio links jumped from eight in mid-1943 to fourteen or fifteen. In 1941 the initial experimental Tunny link was between Berlin and Athens/Salonoka. 
By D-Day in 1944 there were twenty-six links, based on Konigsberg and Straussberg. Other links were usually mobile; in two trucks, one with radio equipment and one with a "send" Tunny machine and a receive "Tunny" machine. The links carried very high-grade intelligence: messages from Hitler and the High Command  to various Army Group commanders in the field.{{sfn|Erskine|Smith|2001|p=353}}{{sfn|Price|2021|p=136}} 

[[Cryptanalysis of the Lorenz cipher]] at Bletchley Park was assisted initially by a machine called [[Heath Robinson (codebreaking machine)|Heath Robinson]] and later by the [[Colossus computer]]s yielded a great deal of valuable high-level intelligence.

{| class="wikitable" | border=1 | style="margin: 1em auto 1em auto"
|+ Bletchley Park names of Tunny links<ref>{{ Harvnb | Copeland | 2006 | p = 41 }}</ref>
|-
! width="100pt" align="center" | Name
! width="200pt" colspan="2" align="center"  | Between
|-
| Bream  || Berlin  || width="100pt" | 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
|-
| Codfish || Berlin || Salonika
|-
|}
Tunny decrypts provided high-grade intelligence in an unprecedented quality. 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'.<ref>S. Wylie, Breaking Tunny and the birth of Colossus, ''Action This Day'' (eds. M. Smith and R. Erskine), Bantam Press, London, 2001, pp. 317-341.</ref>

===Sturgeon===
This was the name given to traffic encoded with the [[Siemens and Halske T52]] ''Geheimschreiber''.<ref>{{ Harvnb | Weierud | 2006 | pp=307–327 }}</ref><ref>{{ Harvnb | Smith | 2006 | p = 35 }}</ref> 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.<ref>{{ Harvnb | McKay | 2006 | pp = 328–333 }}</ref>  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===
This was the name used for traffic enciphered on a ''Geheimschreiber'' that was probably the Siemens T43 [[One-time pad|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 staff  involved at Bletchley Park ==
Including both executives and cryptographers on FISH (Tunny) in the [[Testery]].

: [[Ralph Tester]] —    linguist and head of the ''Testery''

* [[Peter Benenson]] —  codebreaker 
* John Christie —       codebreaker 
* Tom Colvill —         general manager 
* Peter Edgerley —      codebreaker 
* Peter Ericsson —      shift-leader, linguist and senior codebreaker 
* [[Peter Hilton]] —    codebreaker and mathematician 
* [[Roy Jenkins]] —     codebreaker and later cabinet minister 
* Victor Masters —      shift-leader 
* [[Max Newman]] —      mathematician and codebreaker who later set up the [[Newmanry]]
* Denis Oswald —        linguist and senior codebreaker 
* [[Jerry Roberts]] —   shift-leader, linguist and senior codebreaker
* John Thompson —       codebreaker 
* [[John Tiltman]] —    senior codebreaker and intelligence officer 
* [[Alan Turing]] -     mathematician, mainly on ''Enigma'' traffic
* [[W.T. Tutte]] —      codebreaker and mathematician

==See also==
* [[Colossus (computer)]]
* [[Heath Robinson (codebreaking machine)]]
* [[TICOM]]
* [[Turingery]]

==Notes==
{{Reflist|2}}

==References==
{{refbegin}}
* {{Citation | last = Bauer | first = Friedrich L. | author-link = Friedrich L. Bauer | title = Origins of the Fish Cypher Machines | year = 2006 }} in {{Harvnb|Copeland|2006|pp=411–417}}
* {{ Citation | date = 2006 | editor-last = Copeland | editor-first = B. Jack | editor-link = Jack Copeland | title = Colossus: The Secrets of Bletchley Park's Codebreaking Computers | location = Oxford | publisher = Oxford University Press | isbn = 978-0-19-284055-4 }}
* {{Citation | last1 = Deavours | first1 = Cipher A. | last2 = Kruh | first2 = Louis | title = Appendix Mechanics of the German Telecipher Machine | journal = Cryptologia | volume = 10 | issue = 4 | pages = 230–242 |date=October 1986 | doi=10.1080/0161-118691861074}} (reprinted in Cryptology: Yesterday, Today and Tomorrow, Artech House, Norwood, 1987) 
*{{cite book |title= Action this Day |last1= Erskine |first1=  Ralph |last2= Smith|first2= Michael |year= 2001  |publisher= Bantam Press |location= London  |isbn= 0593-049101  }}
* {{Citation | editor-last = Erskine | editor-first = Ralph | editor2-last = Smith | editor2-first = Michael | editor2-link = Michael Smith (newspaper reporter) | title = The Bletchley Park Codebreakers | publisher = Biteback Publishing Ltd | year = 2011 | isbn = 978-1-84954-078-0}} Updated and extended version of ''"Action This Day''" 
* {{ Citation | last = Gannon | first = Paul | date = 2006 | title = Colossus: Bletchley Park's Greatest Secret | location = London | publisher = Atlantic Books | isbn = 978-1-84354-331-2 }}
* {{ Citation | last = Lewin | first = Ronald | year = 2001 | orig-year = 1978 | title = Ultra Goes to War: The Secret Story | series = Classic Military History | location = Harmondsworth, England | publisher = Penguin Books |isbn=9780141390420}}
* {{Citation | last = Mache | first = Wolfgang W. | title = Geheimschreiber | journal = Cryptologia | volume = 10 | issue = 4 |date=October 1986 | doi=10.1080/0161-118691861065 | pages=230–242}} (Reprinted in: Cryptology: Yesterday, Today and Tomorrow, Artech House, Norwood, 1987)
* {{Citation | last = Mache | first = Wolfgang W. | title =  The Siemens Cipher Teletype in the History of Telecommunications | journal = Cryptologia | volume = 13 | issue = 2 |date=April 1989 | doi=10.1080/0161-118991863817 | pages=97–117}} (reprinted in Selections from Cryptologia: History, People, and Technology, Artech House, Norwood, 1998)
* {{ Citation | last = McKay | first = Craig | date = 2006 | contribution = German Teleprinter Traffic and Swedish Wartime Intelligence | editor-last = Copeland | editor-first = B Jack | editor-link = Jack Copeland | title = Colossus: The Secrets of Bletchley Park's Codebreaking Computers | location = Oxford  | publisher = Oxford University Press  | isbn = 978-0-19-284055-4 }}
*{{cite book |last= Price |first= David A.  |title= Geniuses War: Bletchley Park, Colossus, and the Dawn of the Digital Age  |accessdate=  |edition=  |orig-date=  |year= 2021 |publisher= Alfred A Knopf  |location= New York |isbn= 978-0525521549 |oclc= |page= |pages=  }} 
* {{ Citation | last = Smith | first = Michael | author-link = Michael Smith (newspaper reporter) | date = 2006 | contribution = How it began: Bletchley Park Goes to War | editor-last = Copeland | editor-first = B Jack | editor-link = Jack Copeland | title = Colossus: The Secrets of Bletchley Park's Codebreaking Computers | location = Oxford  | publisher = Oxford University Press  | isbn = 978-0-19-284055-4 }}
* {{ Citation | last = Weierud | first = Frode | date = 2006 | contribution = Bletchley Park's Sturgeon—The Fish That Laid No Eggs | editor-last = Copeland | editor-first = B Jack | editor-link = Jack Copeland | title = Colossus: The Secrets of Bletchley Park's Codebreaking Computers | location = Oxford  | publisher = Oxford University Press  | isbn = 978-0-19-284055-4 }}
{{refend}}

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