Review of The Bletchley Park Codebreakers by Ralph Erskine and Michael Smith

Click to increase image sizeClick to decrease image size

Notes

¹In 1947, after his service at Bletchley Park, Simpson began a career in the Civil Service. He retired in 1982.

²Scott was reading mathematics at Brasenose College, Oxford, and was recommended by his tutor Theodore Chaundy for a position at Bletchley Park. Scott began serving at Bletchley Park in 1943 and was assigned to Hut 7 to work on the Japanese merchant ship cipher JN-11 [8].

³Loewe, who had been reading Classics, reported on February 2, 1942, to the Inter-Service Special Intelligence School at Bedford to begin a six-month course in Japanese for a position at Bletchley Park. His article describes the process of “book building” the Japanese codebooks.

⁴Denham was reading Classics at Jesus College, Cambridge, when he was recruited to serve at Bletchley Park. He reported on February 2, 1942, and began the Inter-Service Special Intelligence School at Ardour House, the Gas Company's corner site in Bedford. Denham's chapter in [3, pp. 276–281] describes several of the Japanese ciphers and how the additive superencipherment of JN-25 was done.

⁵Stripp was reading Classics at Trinity College, Cambridge, when he was recruited to serve at Bletchley Park by his tutor Kitson Clark. Stripp was a student in the fifth Japanese language course at Bedford, August 31, 1943–February 18, 1944.

⁶Marshall Hall, Jr. was one of the cryptologic mathematicians who served at the US Naval Communications Annex in Washington, DC, during World War II [2]. Hall visited Bletchley Park from January to July 1944. (p. 130)

⁷JN-25 codegroups consisted of five digits. For error-detection, the sum of the five digits was divisible by 3. A codegroup was said to “scan” if the sum of the five digits was divisible by 3; it was, therefore, a potential true codegroup.

⁸The addition used to superencipher was “noncarrying” addition.

⁹Cassels became a mathematics student of Louis Mordell at Trinity College, Cambridge, after World War II. He received his PhD in 1949. In 1967 he was appointed as Sadleirian Professor of Pure Mathematics at Cambridge. He retired in 1984.

¹⁰An excellent (twenty-four page) description of Banburismus is “All You Ever Wanted to Know About Banburismus but were Afraid to Ask” by Steven Hosgood. http://tallyho.bc.nu/~steve/banburismus.html Accessed March 2, 2011.

¹¹A quick internet search did not yield much information on this topic except the paper by Simpson in Significance [9]. There are some references to the modern use of Bayesian statistics in intelligence. A July 3, 2010, blog by John Graham-Cumming “Bayes, Bletchley, JN-25 and a ‘modern’ optimization” http://blog.jgc.org/2010/07/bayes-bletchley-jn-25-and-modern.html discusses a bit more the ideas in Simpson's Significance article.

Additional information

Notes on contributors

Chris Christensen

Chris Christensen teaches mathematics and cryptology at Northern Kentucky University. He is a member of the ORESME (Ohio River Early Sources in Mathematical Exposition) Reading Group which brings together scholars interested in the history of mathematics from the Cincinnati tri-state area twice a year since 1998 to read original source materials in mathematics. The organization was named after the French Scholastic philosopher Nicole Oresme (1323–1382) whose “latitude of forms” constituted early graphical representations of mathematical functions, long before Descartes.