The Turing Bombe in Action - Bletchley Park - 28th July 2012

A memorable talk by Tony Jarvis showing how the Turing Bombe was used to crack the ring settings on the German Enigma encipherment machine during the Second World War. Unlike the brilliant Polish Bomba (which due credit must be given to Marian Rejewski and his team) in use around 1938, which used 'brute force' to check the ring settings on Enigma, this version of the machine reduced the assumptions of wheel order and scrambler positions that required 'further analysis' to a manageable number via means of a 'crib', or an informed guess as to a known phrase included in the encyphered message. This approach was required after refinements in both the Enigma machine design and its use which made the Polish Bomba brute force attacks impractical. Although the logic of the Bombe was built on Turing's mathematical ideas, an important refinement was made by Gordon Welchman. This refinement was the 'Diagonal Board' which attacked Enigma's stecker board settings. The original Bombes were maufactured by the British Tabulating Machine Company, undet the engineering design of Harold Keene. As far as can be ascertained, all Bombes were destroyed after the war. The bombe in this film (called 'Phoenix') was reconstructed by hand over a period of many years. For further information on the Bomb and its use check out these sites: http://en.wikipedia.org/wiki/Bombe (this also contains an excellent introduction to how Enigma works); http://en.wikipedia.org/wiki/Bomba_%28cryptography%29 (for information on the Polish Bomba); http://www.jharper.demon.co.uk/bombe1.htm (a brilliant site covering the bombe reconstruction project). This film replaces a very tawdry and poor quality filmed lecture (which was both useless in both visual quality and lecture content) that I originally made in 2004. This film is my small contribtuion to the Alan Turing centenary year, and a tiny tribute to the men and women of Bletchley Park and beyond, whose wartime services helped shorten World War Two by at least two years, and probably saved my father's life on more than one occasion. Apologies for the variation in lip-sync. This was caused by having a memory chip of insufficient speed installed in the camera. However the ooprtunity of recording this talk was far too good to miss, and I hope that the problems do not detract too much from your enjoyment of this film. Video Copyright Graham High via Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) ghigh84@gmail.com www.bletchleypark.org.uk www.tnmoc.org