Computer Security and Cryptography

6.7 ARTHUR SCHERBIUS

On January 24, 1928, the United States Patent Office issued U.S. Patent 1,657411 to Arthur Scherbius for his invention, a Ciphering Machine (Fig. 6.6). Scherbius's patent was assigned to Chiffriermaschin Aktiengesellschaft of Berlin. (Note, chiffrier is the German verb to encipher, Aktiengesellschaft is German for joint stock company, which has a meaning similar to Inc. in the United States and Lfd. in England.) The components of the Enigma machine, shown in Figure 6.7, include (1) input device (keyboard), (5) input/output contact plate, (6–9) four rotors, (11) stator (stationary rotor), and (12) output device (lamps). Scherbius called his cipher machine, the Enigma machine. Webster's New Collegiate Dictionary defines enigma as “An obscure saying; a riddle. Anything inexplicable; puzzling.” Scherbius's use of enigma may have been derived from Sir Edward Elgar's 1898 musical composition Enigma Variations. Elgar wrote that the basic theme in G minor was a variation on another piece of music not revealed: “The Enigma I shall not explain – it's ‘dark saying’ must be left unguessed”.

Figure 6.6 The Enigma machine (Courtesy of NSA).

Figure 6.7 U.S. Patent 1,657,411: The Enigma machine.

6.7.1 Scherbius's Reflecting Rotor

The Enigma machine uses rotors, but in a different ...