The Enigma machine looked like a clunky typewriter inside a wooden box, but it was one of the most fearsome code-making devices ever built. Germany used Enigma machines in World War II to scramble military messages. When a soldier typed a letter, internal rotors spun and lit up a different letter - making the message look like random gibberish.
The terrifying part was the sheer number of possible settings. With the rotors, plugboard wires and ring positions all working together, Enigma had about 159 quintillion combinations - that’s 159 followed by 18 zeros. Even if you could check a million settings per second, it would take much longer than the lifetime of the universe to try them all.
To make it worse, the Germans changed the settings at midnight every single day. Codebreakers at Bletchley Park in England had to crack a brand new code in just 24 hours. Using machines called bombes and clever shortcuts, they often did it - and historians think their work shortened World War II by around two years.
