The BBC News site is reporting that the UK Government Communication Headquarters [GCHQ] has released two papers by Alan Turing on the mathematical theory of cryptanalysis (code breaking). (GCHQ is roughly analogous to the US National Security Agency.) The papers had been classified since Turing wrote them, approximately 70 years ago, apparently while he was working at Bletchley Park.
The papers, one entitled The Applications of Probability to Crypt, and the other entitled Paper on the Statistics of Repetitions, discuss mathematical approaches to code breaking.
A GCHQ mathematician said the fact that the contents had been restricted “shows what a tremendous importance it has in the foundations of our subject”
According to the BBC report, the papers have been given to the UK National Archives, although the news does not seem to have made it onto the Archives’ site yet.
(There is one small aspect of the BBC’s article that I found amusing. It has an image of a small section of a page from one of the papers, with the notation, “The papers are typed but contain hand written notes, tables and formulae.” Well, yes. That is the way we produced technical papers back in the days of stone tools.)
The release of these papers is timely, too, in this year which marks the centenary of Turing’s birth. It is good to see that his many contributions in mathematics and computer science are being recognized.
Random Walks 
[…] Last October, I posted a note here about the upcoming 100-year anniversary of the birth of Alan Turing, the English mathematician and pioneer computer scientist. Turing was a central figure in the successful British effort, at Bletchley Park, to break coded messages produced by the Germans’ Enigma cipher machine. Some of Turing’s theoretical papers on cryptanalysis have been declassified only recently. […]