Key (cryptography)

A key is a piece of information that controls the operation of a cryptography algorithm. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa during decryption. Keys are also used in other cryptographic algorithms, such as digital signature schemes and keyed-hash functions (also known as MACs), often used for authentication.

Related Topics:
Cryptography - Encryption - Plaintext - Ciphertext - Decryption - Digital signature - MAC - Authentication

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For a well-designed algorithm, enciphering the same plaintext but with a different key should produce a totally different ciphertext. Similarly, decrypting ciphertext with the wrong key should produce random-looking gibberish. (For deniable encryption, 2 keys can produce 2 very different normal-looking plaintexts). If the decryption key is lost, encrypted data should not in practice be recoverable — at least for high quality encryption algorithms and large enough key sizes.

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