Enigma machine

The Enigma machine emerged from the collision of two forces in post-World War I Germany: the demonstrated vulnerability of wartime communications to interception, and the maturation of electromechanical engineering. Arthur Scherbius, a German electrical engineer, filed his patent on February 23, 1918, for a cipher machine using rotating wired wheels—what cryptographers now call a rotor machine.

Scherbius had studied electricity at technical colleges in Munich and Hanover, founding the firm Scherbius & Ritter in 1918. His invention combined established concepts—polyalphabetic substitution ciphers dating to the Renaissance, and electrical switching from telephone exchanges—into something new: a machine that could produce astronomical numbers of possible encryption keys.

The commercial version launched in 1923, marketed to businesses wanting secure communications. Scherbius initially failed to interest the military, so he targeted international commerce instead. The name 'Enigma,' Greek for 'riddle,' captured the machine's promise of impenetrable secrets.

The German Navy adopted a modified Enigma in 1926, followed by the Army and Air Force. Each service used different configurations, and operational security procedures added complexity. With three or more rotors, a plugboard, and daily key changes, the machine could produce 158 quintillion possible settings—a number that seemed to guarantee unbreakable encryption.

But Enigma contained a fatal cryptographic flaw built into its design: the reflector mechanism that made the machine self-reciprocal (pressing A might produce B, and pressing B would produce A) also meant that no letter could ever encrypt to itself. This seemingly minor constraint significantly reduced the possibility space and became the foothold that Polish, and later British, codebreakers exploited.

Scherbius died in a horse carriage accident in 1929, never seeing his invention's role in the war that would come. The path dependence established by Enigma's design flaws would shape World War II: Polish mathematicians cracked early versions by 1932, their techniques passed to the British, who built Colossus at Bletchley Park—arguably the first programmable electronic computer—specifically to break more complex Enigma variants.