View source for Gordon Welchman (nonfiction)

[[File:Gordon_Welchman.jpg|thumb|William Welchman.]]'''William Gordon Welchman''' (15 June 1906, Bristol, England – 8 October 1985, Newburyport, Massachusetts, US) was a British [[Mathematician (nonfiction)|mathematician]], university professor, Second World War codebreaker at Bletchley Park and author.

Just before the Second World War, Welchman was invited by Commander Alastair Denniston to join the Government Code and Cypher School at Bletchley Park, in the event of war. He was one of four early recruits (the others being [[Alan Turing (nonfiction)|Alan Turing]], Hugh Alexander and [[Stuart Milner-Barry (nonfiction)|Stuart Milner-Barry]]), who all made significant contributions at Bletchley and who became known as "the wicked uncles". They were also the four signatories to an influential letter, delivered to Winston Churchill in October 1941, asking for more resources for the code-breaking work at Bletchley Park. Churchill responded with one of his "Action This Day" written comments.

As stated in his book, most of his work at Bletchley was centred on what was known as "traffic analysis" of encrypted German communications. This is roughly described as the practice of examining parts of messages that are standardized descriptors or headers, such as message origination, message destination, time/date information, and so on. Most cryptographers agree this is markedly easier than attacking cryptographic ciphers directly (although still very complicated and mathematically intensive processing is needed to make initial discoveries), and Welchman is credited with innovating the approach. This led to data analysis techniques that today we describe as metadata analysis.

Welchman envisaged an enhancement to Alan Turing's improved design of the Polish electromechanical Enigma cipher-breaking machine, the bombe. Welchman's enhancement, the "diagonal board", made the device substantially more efficient in the attack on ciphers generated by the German Enigma machine. 

Welchman was head of Hut Six, the section at Bletchley Park responsible for breaking German Army and Air Force Enigma ciphers. During his time at Bletchley, Welchman opposed engineer [[Tommy Flowers (nonfiction)|Tommy Flowers]]' efforts on the [[Colossus computer (nonfiction)|Colossus computer]] (the world's first programmable electronic computer) because Colossus used vacuum tubes.

After the war he moved to the US, and later took American citizenship.

Welchman became a naturalised US citizen in 1962. In that year, he joined the [[MITRE Corporation (nonfiction)|MITRE Corporation]], working on secure communications systems for the US military. He retired in 1971, but was retained as a consultant.

In 1982 his book ''The Hut Six Story'' was published, initially by McGraw-Hill in the US and by Allen Lane in Britain. The National Security Agency disapproved. The book was not banned, but Welchman lost his security clearance (and therefore his consultancy with MITRE) and was forbidden to discuss either the book or his wartime work.

== In the News ==

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== Fiction cross-reference ==

* [[Crimes against mathematical constants]]
* [[Gnomon algorithm]]
* [[Gnomon Chronicles]]
* [[Mathematician]]
* [[Mathematics]]

== Nonfiction cross-reference ==

* [[Colossus computer (nonfiction)]]
* [[Tommy Flowers (nonfiction)]]
* [[Mathematics (nonfiction)]]
* [[Stuart Milner-Barry (nonfiction)]]
* [[MITRE Corporation (nonfiction)]] - an American not-for-profit organization based in Bedford, Massachusetts, and McLean, Virginia. It manages federally funded research and development centers (FFRDCs) supporting several U.S. government agencies.

External links:

* [https://en.wikipedia.org/wiki/Gordon_Welchman Gordon Welchman] @ Wikipedia
* [https://en.wikipedia.org/wiki/Mitre_Corporation MITRE Corporation] @ Wikipedia

[[Category:Nonfiction (nonfiction)]]
[[Category:Cryptographers (nonfiction)]]
[[Category:Mathematicians (nonfiction)]]
[[Category:People (nonfiction)]]