The German Enigma Machine may be the most famous encryption device of the Second World War, but it was by no means the only one. In 1937, the Japanese developed the "97-shiki O-bun In-ji-ki" or "97 Alphabetical Typewriter," named for its creation on the Japanese year 2597. This device was better known by its U.S. code-name: "Purple".
The machine consisted of two typewriters and an electrical rotor system with a 25-character alphabetic switchboard. Like the Enigma machine that inspired it, a plaintext, or unencrypted message, could be manually inputted. But its main innovation was the second electric typewriter, which would print the encrypted message onto a piece of paper (Enigma presented text in the form of blinking lights). Thus, only one person was needed to operate it. And because the Japanese changed the key on a daily basis, codebreakers weren't able to find patterns in the messages. As Alberto Perez notes, "The switchboard contained 25 connections, which could be arranged into 6 pairs of connections, producing 70,000,000,000,000 possible arrangements." Incredibly, U.S. code breakers found a way to crack the machine.