How Alan Turing and Bletchley Park Broke the Nazis' Enigma Code

In the early 1920s, the Enigma machine was commercially available from Germany, allowing any organization to purchase encryption devices. The German Navy, Army, and Air Force quickly adopted it, enabling rapid, secret coordination for blitzkrieg tactics. The machine used interchangeable rotors and a plugboard that expanded possible keys to 7 x 10^18. Alan Turing, already known for the Turing machine, was recruited by Britain's wartime codebreaking headquarters at Bletchley Park. There he identified flaws in Enigma's design, such as its inability to encrypt a letter as itself, and exploited predictable operator behavior like weather reports. To process all possibilities, a non-theoretical computation engine called the Bombe was built. The intelligence it produced contributed to the success of the D-Day invasion and may have shortened World War II by years. A new Veritasium video explains the Enigma's inner workings.