key

An input parameter used to vary a transformation function performed by a cryptographic algorithm. (See: private key, public key, storage key, symmetric key, traffic key. Compare: initialization value.)

Used in singular form as a collective noun referring to keys or keying material. Example: A fill device can be used transfer key between two cryptographic devices.

An input parameter used to vary a process that determines patterns for an anti-jam measure. (See: frequency hopping, spread spectrum.)

Tutorial: A key is usually specified as a sequence of bits or other symbols. If a key value needs to be kept secret, the sequence of symbols that comprise it should be random, or at least pseudorandom, because that makes the key harder for an adversary to guess. (See: brute-force attack, cryptanalysis, strength.)