Editing Alan Turing (section)

===Cryptanalysis===
During the Second World War, Turing was a leading participant in the breaking of German ciphers at [[Bletchley Park]]. The historian and wartime codebreaker [[Asa Briggs]] has said, "You needed exceptional talent, you needed genius at Bletchley and Turing's was that genius."<ref>{{Cite AV media | last = Briggs | first = Asa | author-link = Asa Briggs | title = Britain's Greatest Codebreaker | type = TV broadcast | publisher = [[Channel 4|UK Channel 4]] | date = 21 November 2011}}</ref>

From September 1938, Turing worked part-time with the [[Government Code and Cypher School]] (GC&CS), the British codebreaking organisation. He concentrated on [[cryptanalysis of the Enigma|cryptanalysis of the Enigma cipher machine]] used by [[Nazi Germany]], together with [[Dilly Knox]], a senior GC&CS codebreaker.<ref>{{Cite book | author-link = Jack Copeland | last = Copeland | first = Jack | chapter = Colossus and the Dawning of the Computer Age | page = 352 | title = Action This Day | publisher = Bantam | date = 2001 | isbn = 978-0-593-04910-5 | editor1-first = Michael | editor1-last = Smith | editor2-first = Ralph | editor2-last = Erskine }}</ref> Soon after the July 1939 meeting near [[Warsaw]] at which the [[Polish Cipher Bureau]] gave the British and French details of the wiring of [[Enigma rotor details|Enigma machine's rotors]] and their method of decrypting [[Enigma machine]]'s messages, Turing and Knox developed a broader solution.<ref>{{Harvnb|Copeland|2004a|p=217}}</ref> The Polish method relied on an insecure [[Cryptanalysis#Indicator|indicator]] procedure that the Germans were likely to change, which they in fact did in May 1940. Turing's approach was more general, using [[Cryptanalysis of the Enigma#Crib-based decryption|crib-based decryption]] for which he produced the functional specification of the [[bombe]] (an improvement on the Polish [[Bomba (cryptography)|Bomba]]).<ref>{{cite news |last=Clark |first=Liat |url=https://www.wired.co.uk/news/archive/2012-06/18/turing-contributions?page=all |title=Turing's achievements: codebreaking, AI and the birth of computer science (Wired UK) |magazine=Wired |date=18 June 2012 |access-date=31 October 2013 |archive-url=https://web.archive.org/web/20131102122933/http://www.wired.co.uk/news/archive/2012-06/18/turing-contributions?page=all |archive-date=2 November 2013 |url-status=live }}</ref>

[[File:Turing flat.jpg|thumb|right|Two cottages in the stable yard at [[Bletchley Park]]. Turing worked here in 1939 and 1940, before moving to [[Hut 8]].]]

On 4 September 1939, the day after the UK declared war on Germany, Turing reported to Bletchley Park, the wartime station of GC&CS.<ref name=Copeland2006p378>Copeland, 2006 p.&nbsp;378.</ref> Like all others who came to Bletchley, he was required to sign the [[Official Secrets Act 1939|Official Secrets Act]], in which he agreed not to disclose anything about his work at Bletchley, with severe legal penalties for violating the Act.<ref name="Collins">{{cite web |last=Collins |first=Jeremy |title=Alan Turing and the Hidden Heroes of Bletchley Park: A Conversation with Sir John Dermot Turing |date=24 June 2020 |location=New Orleans |publisher=The National WWII Museum |url=https://www.nationalww2museum.org/war/articles/alan-turing-betchley-park |access-date=24 August 2021 |archive-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202101721/https://www.nationalww2museum.org/war/articles/alan-turing-betchley-park |url-status=live }}</ref>

Specifying the bombe was the first of five major cryptanalytical advances that Turing made during the war. The others were: deducing the indicator procedure used by the German navy; developing a statistical procedure dubbed ''[[Banburismus]]'' for making much more efficient use of the bombes; developing a procedure dubbed ''[[Turingery]]'' for working out the cam settings of the wheels of the [[Lorenz SZ 40/42]] (''Tunny'') cipher machine and, towards the end of the war, the development of a portable [[secure voice]] scrambler at [[Her Majesty's Government Communications Centre|Hanslope Park]] that was codenamed ''Delilah''.<ref>{{Cite web |title=How Alan Turing Cracked The Enigma Code |url=https://www.iwm.org.uk/history/how-alan-turing-cracked-the-enigma-code |access-date=12 July 2023 |website=Imperial War Museums |language=en |archive-date=24 January 2022 |archive-url=https://web.archive.org/web/20220124140731/https://www.iwm.org.uk/history/how-alan-turing-cracked-the-enigma-code |url-status=live }}</ref><ref>{{Cite journal |last1=Turing |first1=Alan M. |last2=Bayley |first2=D. |date=2012 |title=Report on Speech Secrecy System DELILAH, a Technical Description Compiled by A. M. Turing and Lieutenant D. Bayley REME, 1945–1946 |url=http://www.tandfonline.com/doi/abs/10.1080/01611194.2012.713803 |journal=Cryptologia |language=en |volume=36 |issue=4 |pages=295–340 |doi=10.1080/01611194.2012.713803 |s2cid=205488183 |issn=0161-1194 |access-date=26 August 2024 |archive-date=12 July 2023 |archive-url=https://web.archive.org/web/20230712092022/https://www.tandfonline.com/doi/abs/10.1080/01611194.2012.713803 |url-status=live }}</ref>

By using statistical techniques to optimise the trial of different possibilities in the code breaking process, Turing made an innovative contribution to the subject. He wrote two papers discussing mathematical approaches, titled ''The Applications of Probability to Cryptography''<ref>{{cite web | last = Turing | first = Alan | year = c. 1941 | title = The Applications of Probability to Cryptography | id = The National Archives (United Kingdom): HW 25/37 | url = http://discovery.nationalarchives.gov.uk/details/r/C11510465 | access-date = 25 March 2015 | archive-url = https://web.archive.org/web/20150407234050/http://discovery.nationalarchives.gov.uk/details/r/C11510465 | archive-date = 7 April 2015 | url-status = live }}</ref> and ''Paper on Statistics of Repetitions'',<ref>{{cite web | last = Turing | first = Alan | year = c. 1941 | title = Paper on Statistics of Repetitions | id = The National Archives (United Kingdom): HW 25/38 | url = http://discovery.nationalarchives.gov.uk/details/r/C11510466 | access-date = 25 March 2015 | archive-url = https://web.archive.org/web/20150408013845/http://discovery.nationalarchives.gov.uk/details/r/C11510466 | archive-date = 8 April 2015 | url-status = live }}</ref> which were of such value to GC&CS and its successor [[GCHQ]] that they were not released to the [[The National Archives (United Kingdom)|UK National Archives]] until April 2012, shortly before the centenary of his birth. A GCHQ mathematician, "who identified himself only as Richard," said at the time that the fact that the contents had been restricted under the Official Secrets Act for some 70 years demonstrated their importance, and their relevance to post-war cryptanalysis:<ref name=bbcrichard>{{cite news |last=Vallance |first=Chris |title=Alan Turing papers on code breaking released by GCHQ |url=https://www.bbc.co.uk/news/technology-17771962 |access-date=20 April 2012 |work=BBC News |date=19 April 2012 |archive-url=https://web.archive.org/web/20121004192554/http://www.bbc.co.uk/news/technology-17771962 |archive-date=4 October 2012 |url-status=live }}</ref>

{{blockquote|text=[He] said the fact that the contents had been restricted "shows what a tremendous importance it has in the foundations of our subject". ... The papers detailed using "mathematical analysis to try and determine which are the more likely settings so that they can be tried as quickly as possible". ... Richard said that GCHQ had now "squeezed the juice" out of the two papers and was "happy for them to be released into the public domain".}}

Turing had a reputation for eccentricity at Bletchley Park. He was known to his colleagues as "Prof" and his treatise on Enigma was known as the "Prof's Book".<ref>{{Harvnb|Hodges|1983|p=208}}</ref><ref>{{cite book |title=The Prof's Book: Turing's Treatise on the Enigma |first=Alan M. |last=Turing |year=1940 |url=https://archive.org/details/hw-25-3/ |url-access=registration |quote=In late 1940 Alan Turing wrote a report describing the methods he and his colleagues at Bletchley Park had used to break into the German Enigma cipher systems. At Bletchley it was known as 'the Prof's Book.' A copy of this handbook was at last released from secrecy by the American National Security Agency in April 1996, under the title ''Turing's Treatise on the Enigma''. Subsequently, a much better original copy was released by the (British) National Archives, box HW 25/3. This also revealed a title which had been lost in the American copy: ''Mathematical theory of ENIGMA machine''. (Though, oddly, the report does not actually have any mathematical theory.)}}</ref> According to historian [[Ronald Lewin]], [[I.J. Good|Jack Good]], a cryptanalyst who worked with Turing, said of his colleague:

{{blockquote|In the first week of June each year he would get a bad attack of hay fever, and he would cycle to the office wearing a service gas mask to keep the pollen off. His bicycle had a fault: the chain would come off at regular intervals. Instead of having it mended he would count the number of times the pedals went round and would get off the bicycle in time to adjust the chain by hand. Another of his eccentricities is that he chained his mug to the radiator pipes to prevent it being stolen.<ref>{{Harvnb|Lewin|1978|p=57}}</ref>}}

[[Peter Hilton]] recounted his experience working with Turing in [[Hut 8]] in his "Reminiscences of Bletchley Park" from ''A Century of Mathematics in America:''<ref>{{Cite web|url=http://www.ams.org/publicoutreach/math-history/hmath1-hilton22.pdf|title=A Century of Mathematics in America, Part 1, Reminiscences of Bletchley Park|last=Hilton|first=Peter|archive-url=https://web.archive.org/web/20190829112241/http://www.ams.org/publicoutreach/math-history/hmath1-hilton22.pdf|archive-date=29 August 2019|url-status=live}}</ref>

{{blockquote| It is a rare experience to meet an authentic genius. Those of us privileged to inhabit the world of scholarship are familiar with the intellectual stimulation furnished by talented colleagues. We can admire the ideas they share with us and are usually able to understand their source; we may even often believe that we ourselves could have created such concepts and originated such thoughts. However, the experience of sharing the intellectual life of a genius is entirely different; one realizes that one is in the presence of an intelligence, a sensibility of such profundity and originality that one is filled with wonder and excitement.
Alan Turing was such a genius, and those, like myself, who had the astonishing and unexpected opportunity, created by the strange exigencies of the Second World War, to be able to count Turing as colleague and friend will never forget that experience, nor can we ever lose its immense benefit to us.|sign=|source=}}

Hilton echoed similar thoughts in the Nova [[PBS]] documentary ''Decoding Nazi Secrets''.<ref>{{Cite web|url=https://www.pbs.org/wgbh/nova/transcripts/2615decoding.html|title=NOVA {{!}} Transcripts {{!}} Decoding Nazi Secrets {{!}} PBS|last=Hilton|first=Peter|website=[[PBS]]|archive-url=https://web.archive.org/web/20190829112240/https://www.pbs.org/wgbh/nova/transcripts/2615decoding.html|archive-date=29 August 2019|url-status=live}}</ref>

While working at Bletchley, Turing, who was a talented [[Long-distance running|long-distance runner]], occasionally ran the {{convert|40|mi}} to London when he was needed for meetings,<ref>{{Cite book | last = Brown | first = Anthony Cave | author-link = Anthony Cave Brown | title = Bodyguard of Lies: The Extraordinary True Story Behind D-Day | page = 19 | publisher=The Lyons Press | year = 1975 | isbn = 978-1-59921-383-5 | url = https://archive.org/details/bodyguardoflies00brow | url-access = registration}}</ref> and he was capable of world-class marathon standards.<ref>{{cite news|url=https://www.theguardian.com/commentisfree/2010/mar/10/alan-turing-2012-olympics|title=An Olympic honour for Alan Turing|author=Graham-Cumming, John|newspaper=The Guardian|date=10 March 2010|location=London|access-date=10 December 2016|archive-url=https://web.archive.org/web/20161201171628/https://www.theguardian.com/commentisfree/2010/mar/10/alan-turing-2012-olympics|archive-date=1 December 2016|url-status=live}}</ref><ref>{{cite web | first=Pat | last=Butcher | url=http://www.globerunner.org/index.php/09/in-praise-of-great-men/ | title=In Praise of Great Men | publisher=Globe Runner | date=14 September 2009 | access-date=23 June 2012 | archive-url=https://web.archive.org/web/20130818145759/http://www.globerunner.org/index.php/09/in-praise-of-great-men/ | archive-date=18 August 2013 | url-status=live }}</ref> Turing tried out for the [[Great Britain at the 1948 Summer Olympics|1948 British Olympic team]], but he was hampered by an injury. His tryout time for the marathon was only 11 minutes slower than British silver medallist [[Tom Richards (athlete)|Thomas Richards]]' Olympic race time of 2 hours 35 minutes. He was Walton Athletic Club's best runner, a fact discovered when he passed the group while running alone.<ref>{{cite web | last1 = Hodges | first1 = Andrew | author-link = Andrew Hodges | title = Alan Turing: a short biography | url = http://www.turing.org.uk/bio/part6.html | publisher = Alan Turing: The Enigma | access-date = 12 June 2014 | archive-url = https://web.archive.org/web/20130914091359/http://www.turing.org.uk/bio/part6.html | archive-date = 14 September 2013 | url-status = live }}</ref><ref>{{cite news | last1 = Graham-Cumming | first1 = John | author-link = John Graham-Cumming | title = Alan Turing: a short biography | url = https://www.theguardian.com/commentisfree/2010/mar/10/alan-turing-2012-olympics | newspaper = The Guardian | date = 10 March 2010 | access-date = 12 June 2014 | archive-url = https://web.archive.org/web/20141108165218/http://www.theguardian.com/commentisfree/2010/mar/10/alan-turing-2012-olympics | archive-date = 8 November 2014 | url-status = live }}</ref><ref>{{cite web | last1 = Butcher | first1 = Pat | title = Turing as a runner | url = http://www-groups.dcs.st-and.ac.uk/~history/Extras/Turing_running.html | publisher = The MacTutor History of Mathematics archive | date = December 1999 | access-date = 12 June 2014 | archive-url = https://web.archive.org/web/20141113020916/http://www-groups.dcs.st-and.ac.uk/~history/Extras/Turing_running.html | archive-date = 13 November 2014 | url-status = live }}</ref> When asked why he ran so hard in training he replied:

{{blockquote|I have such a stressful job that the only way I can get it out of my mind is by running hard; it's the only way I can get some release.<ref>{{cite web |url=https://kottke.org/18/04/alan-turing-was-an-excellent-runner |first=Jason |last=Kottke |title=Turing was an excellent runner |website=kottke.org |date=17 April 2018 |access-date=26 August 2024 |archive-date=9 June 2021 |archive-url=https://web.archive.org/web/20210609192748/https://kottke.org/18/04/alan-turing-was-an-excellent-runner |url-status=live }}</ref>}}

Due to the problems of [[counterfactual history]], it is hard to estimate the precise effect Ultra intelligence had on the war.<ref>See for example {{cite book|last=Richelson|first=Jeffery T.|title=A Century of Spies: Intelligence in the Twentieth Century|date=1997|publisher=Oxford University Press|location=New York|page=296|author-link=Jeffrey T. Richelson}} and {{cite book|last=Hartcup|first=Guy|title=The Effect of Science on the Second World War|date=2000|publisher=Macmillan Press|location=Basingstoke, Hampshire|pages=96–99|author-link=Guy Hartcup}}</ref> However, official war historian [[Harry Hinsley]] estimated that this work shortened the war in Europe by more than two years and saved over 14&nbsp;million lives.<ref name="Hinsley 1996">{{citation | last = Hinsley | first = Harry | author-link = Harry Hinsley | title = The Influence of ULTRA in the Second World War | orig-date = 1993 | year = 1996 | url = http://www.cix.co.uk/~klockstone/hinsley.htm | access-date = 26 August 2024 | archive-date = 15 October 2022 | archive-url = https://web.archive.org/web/20221015210957/https://www.cix.co.uk/~klockstone/hinsley.htm | url-status = live }} Transcript of a lecture given on Tuesday 19 October 1993 at Cambridge University</ref>

At the end of the war, a memo was sent to all those who had worked at Bletchley Park, reminding them that the code of silence dictated by the Official Secrets Act did not end with the war but would continue indefinitely.<ref name="Collins"/> Thus, even though Turing was appointed an [[Order of the British Empire|Officer of the Order of the British Empire]] (OBE) in 1946 by King [[George VI]] for his wartime services, his work remained secret for many years.<ref>{{cite news | title = Alan Turing: Colleagues share their memories | url = https://www.bbc.co.uk/news/technology-18541715 | date = 23 June 2012 | work = BBC News | access-date = 21 June 2018 | archive-url = https://web.archive.org/web/20180707105436/https://www.bbc.co.uk/news/technology-18541715 | archive-date = 7 July 2018 | url-status = live }}</ref><ref name="thegazette.co.uk">{{cite web|url=https://www.thegazette.co.uk/all-notices/content/114|title=This month in history: Alan Turing and the Enigma code|website=thegazette.co.uk|access-date=6 February 2019|archive-url=https://web.archive.org/web/20190626211800/https://www.thegazette.co.uk/all-notices/content/114|archive-date=26 June 2019|url-status=live}}</ref>