Harold Hall "Doc" Keen (1894–1973) was a British engineer who produced the engineering design, and oversaw the construction of, the British bombe, a codebreaking machine used in World War II to read German messages sent using the Enigma machine. He was known as "Doc" Keen because of his habit of carrying tools and paperwork in a case resembling a doctor's bag. After the war he was awarded the O.B.E.
The working rebuilt bombe at Bletchley Park museum. Each of the rotating drums simulates the action of an Enigma rotor. There are 36 Enigma-equivalents and, on the right hand end of the middle row, three indicator drums. John Harper led the 'Phoenix' team that built this. It was officially switched on by the Duke of Kent, patron of the British Computer Society on 17 July 2008.
The bombe was an electro-mechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted secret messages during World War II. The US Navy and US Army later produced their own machines to the same functional specification, albeit engineered differently both from each other and from Polish and British bombes.
A wartime picture of a Bletchley Park Bombe
A three-rotor Enigma with plugboard (Steckerbrett)
The plugboard of an Enigma machine, showing two pairs of letters swapped: S–O and A–J. During World War II, ten plugboard connections were made.
A German Enigma key list with machine settings for each day of one month
