Two papers written during World War II by computing forefather Alan Turing have been released to The National Archives in the UK. The papers, apparently written between 1941 and 1942 while Turing was at Bletchley Park, develop theories of cryptographic analysis and mathematics that were likely used in breaking the German Enigma cipher. For 70 years, the potentially sensitive documents were kept under wraps by GCHQ, the British intelligence agency that deals with information security. Last week, however, GCHQ turned them over to the public domain, saying it had "squeezed the juice" out of the papers.
The first paper, "Paper on Statistics of Repetitions," is apparently a report on testing whether the same key has been used in parts of multiple cipher messages. The second, "The Applications of Probability to Cryptography," uses a variety of real-life examples to determine how probability might be applied to breaking codes. It's one of these examples that has allowed GCHQ to determine the age of the undated papers: a section on calculating life expectancy includes the note that "Hitler is now of age 52." The papers can be ordered online from The National Archives or visited in person. Many of Turing's other papers can already be found on the Turing Digital Archive.