Update to
Alan Turing: the Enigma

by Andrew Hodges

Bridge Passage

Alan Turing: the Enigma

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Page 242: AMT's arrival in New York without identifying papers is clearly described in his own report written two weeks later. See this transcript. This replaces my note BP.2.

Page 243: AMT disparaged the existing group of U. S. Navy cryptanalysts: see the same transcript. His own remarks amply bear out the hint made by his mother (see my note BP.4). However, the arrival of high-calibre mathematicians like Gleason showed that a rapid change was taking place.

Page 244: In 1983 I had only heard a rumour of AMT having gone 'to Ohio' on a mission and did not include mention of it. The rumour was correct: in December 1942 he visited the National Cash Register factory at Dayton, Ohio, where the new American Bombes were being built. See his report. There may also have been another visit later.

Page 245: AMT's report also makes it clear that the question of what he was allowed to see, especially regarding American speech secrecy developments, had never been properly agreed. Further reports show that the agreement entailed that he must not say anything to British authorities that would reveal the American developments he had seen, and that this constraint was taken completely seriously. All this only adds weight to the question of what the US would have thought of his 'security risk' status in 1952.

The excellent analysis of this period in The Ultra-Magic Deals, Bradley E. Smith (1993) brings out that the question of Turing's access to speech secrecy work at Bell Laboratories triggered an enormous row between the British and American agencies. Furthermore, this episode was important in prompting a more comprehensive 'BRUSA' intelligence-sharing agreement in 1943. The Anglo-American institutional structures created by this agreement have essentially continued for sixty years to shape the global order.

Page 253, footnote: The student of Scholz was Gisbert Hasenjäger, who after the war became a distinguished figure in mathematical logic. In 1999 he was shown interviewed on television (for Station X). According to F. L. Bauer's excellent Decrypted Secrets, it was Hasenjäger, then 23, who was responsible for the security of the Enigma systems. Bauer comments that he 'totally overlooked' the possibility of the logic of the Bombe. According to the report by Klaus Schmeh (2005), he was most impressed that 'Der grosse Alan Turing' had been his opponent.

There is further material in the Alan Turing Internet Scrapbook: Alan Turing as US-UK link

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