Cipher machines are devices used to encrypt and decrypt messages, ensuring that only authorized users can read the information. They work by transforming plain text into coded text using various algorithms and keys. This process helps protect sensitive data from unauthorized access, making it essential for secure communication. Historically, cipher machines have played a crucial role in military and diplomatic communications. Notable examples include the Enigma machine, used by the German military during World War II, and the SIGABA, employed by the United States. These machines laid the groundwork for modern cryptography and secure digital communication.