GCHQ, the UK government's communications headquarters, has published a set of code-breaking papers written by Alan Turing during WWII. The papers had been held in secret since they were written. The papers are c"The Applications of Probability to Crypt" and "Paper on the Statistics of Repetitions" and they deal with cryptanalysis techniques to optimize breaking Nazi ciphers. They're displayed at the National Archives at Kew. The BBC has more:
According to the GCHQ mathematician, who identified himself only as Richard, 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".