Enigma machine. The Enigma machine was a German electromechanical device used in World War 2 to encrypt messages. After setting up the machine, messages were typed into the keyboard (across bottom) and a series of letters on the display above would light up, providing the encrypted version. A system of rotors (upper centre) meant that each letter could be enciphered as any other character (except itself). This is the four-rotor version, used by the German navy to communicate with U-boats (submarines). Enigma messages were deciphered by the Allies at Bletchley Park, England.