World_War_II_.E2.80.93_British_bombes Harold_Keen

the working rebuilt bombe @ bletchley park museum. each of rotating drums simulates action of enigma rotor. there 36 enigma-equivalents and, on right hand end of middle row, 3 indicator drums. john harper led phoenix team built this. officially switched on duke of kent, patron of british computer society on 17 july 2008.

a machine called cryptologic bomb (polish: bomba kryptologiczna) had been produced polish codebreakers in successful breaking of enigma before 1939. was, useful long germans continued particular weaknesses in operating procedure, gradually tightened up, polish success rate diminished dramatically. alan turing designed british bombe on more general principle, assumption of presence of text, called crib, cryptanalysts predict present @ defined point in message. technique termed known plaintext attack , had been used limited extent poles, e.g., germans use of anx — german to, followed x spacer.

as chief engineer @ british tabulating machine company @ letchworth keen approached turn these ideas working reality. first bombe, based on turing s original design, installed in hut 1 @ bletchley park on 18 march 1940 , named victory . second bombe, named agnus dei , later shortened agnes , or aggie , equipped important additional feature, diagonal board had been designed gordon welchman. installed on 8 august 1940; victory later returned letchworth have diagonal board fitted.

during 1940, 178 messages broken on 2 machines, successfully. because of danger of bombes @ bletchley park being lost if there bombing raid, 5 bombe outstations established, @ adstock, gayhurst, wavendon, stanmore, , eastcote. bombe referred group captain winterbotham bronze goddess because of colour. devices more prosaically described operators being great big metal bookcases .