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
The bomba, or bomba kryptologiczna, was a special-purpose machine designed around October 1938 by Polish Cipher Bureau cryptologist Marian Rejewski to break German Enigma-machine ciphers.
Diagram of Rejewski's cryptologic bomb. For clarity, only one set of three rotors is shown (1); in reality, there were six such sets. An electric motor (2) turns the rotors. 3: Switches.
Enigma's plugboard, with two cables connected (ten were used during World War II). This enhancement greatly increased the system's security.