Four-rotor Enigma cryptography machine. This device was an electromechanical German encryption machine used in World War II (1939-1945). Messages were typed into the keyboard and a series of letters would light up on the display, providing the encrypted version (the ciphertext). A system of rotors meant that each letter could be enciphered as any other, except itself. Enigma was the German's main coding device, and was mainly used to direct their submarines to attack enemy shipping convoys. The four-rotor machine was used by the German Navy from 1 February 1943. This specific machine was used for communications between Germany and Japan. The code was eventually deciphered by the Allies, by researchers working at Bletchley Park, UK. Photographed at The National Museum of the U.S. Navy, Washington DC, USA.