Cipher device

A cipher device (or cipher machine, cipher box, crypto box) is a physical cryptographic device used to encrypt and decrypt messages between plaintext (unencrypted) and ciphertext (encrypted or secret) forms. The ciphertext is suitable for transmission over a channel, such as radio, that might be observed by an adversary the communicating parties wish to conceal the plaintext from.

Mechanical and electromechanical devices have been used as cipher devices, but modern implementations are digital devices.

Modern devices

In order to provide its main functionalities (encryption and decryption), a modern cipher device relies on subfunctionalities such as random number generation, key establishment, digital signature generation and verification, and message authentication, each of which is implemented by a cryptographic module, which is implemented as hardware, software, and/or firmware.

Modern cipher devices are a part of a cryptographic service, which, as a whole, provides confidentiality, integrity, source authentication, entity authentication, non-repudiation support, access control, and availability. Most cryptographic services are owned and operated by nation-states.

See also

• Cryptography