The Enigma cipher machine was a mechanical cipher machine used by Germany during World War II. It employs complex rotation mechanisms and electrical circuits for encrypting and decrypting sensitive military communications. Composed of a set of rotating wheels, each wheel has 26 letters. By rotating the wheel and establishing electrical connections, the input letters are replaced and swapped multiple times, and finally encrypted letters are output. It is also equipped with a power strip, which can further increase the complexity of passwords. The complexity and variability of its design made it one of the most advanced encryption devices at that time. But it was eventually successfully cracked by the Allies, becoming an important milestone in the history of cryptography.