"The science of cryptography is very elegant ...the ends for which it's used is less elegant."
James Sanborn, sculptor
In 1926 the German Army adopted a supposedly impenetrable electro-mechanical encryption device that eventually proved their undoing in World War II. Eight years earlier, electrical engineer Arthur Scherbius (1878-1929) had developed the first model of the Enigma machine, a bulky contraption incorporating a full-sized typewriter and three rotors to code messages. When typing a letter, the first one of these electrical discs rotated and caused .the next one to do likewise, similar to the wheels in an odometer. Wires connecting the rotors provided an electrical path from the keys on the typewriter to the output end plate, with the various connections in between ensuring that the final product of the plaintext input was ciphered.
However, the army deemed Scherbius's initial 110- pound (50 kg) Enigma A and B to be insufficiently secure, and hence did not acquire them. To guarantee that messages sent from the machine were not decipherable, the inventor created a safety device for his third model that distinguished his by now smaller and lighter apparatus from all the other rotor encryption machines of the time: a reflector. Stuck behind the last rotor, the reflector gathered pairs of signals sent from the keyboard and then returned the currents as single, unified signals through the rotors.
The Nazis considered the reflector-assisted Enigma—whose messages were decrypted in the same way they were encrypted—undecipherable. However, the flaw of the reflector was that the machine's output was never the same as the input, that is, "a" could never be encrypted as "a." When British cryptologists became aware of this fact, and identified recurrent use of standard German phrases (such as "Heil Hitler") in the messages, they were able to decipher the codes and turn the war around.
