A parameter used in conjunction with a cryptographic algorithm that determines the specific operation of that algorithm.
Source(s):
FIPS 201-3 under Cryptographic Key

  A numerical value used to control cryptographic operations, such as decryption, encryption, signature generation, or signature verification. Usually a sequence of random or pseudorandom bits used initially to set up and periodically change the operations performed in cryptographic equipment for the purpose of encrypting or decrypting electronic signals, or for determining electronic counter-countermeasures (ECCM) patterns, or for producing other key.
Source(s):
CNSSI 4009-2015 from CNSSI 4005

  A parameter used in conjunction with a cryptographic algorithm that determines its operation. Examples applicable to this Standard include: 1. The computation of a digital signature from data, and 2. The verification of a digital signature.
Source(s):
NIST SP 800-12 Rev. 1 under Key from FIPS 186-4

  A parameter used in conjunction with a cryptographic algorithm that determines its operation. Examples applicable to this Recommendation include: 1. The computation of a digital signature from data, and 2. The verification of a digital signature.
Source(s):
NIST SP 800-102 under Key

  A parameter used with a cryptographic algorithm that determines its operation in such a way that an entity with knowledge of the key can reproduce or reverse the operation, while an entity without knowledge of the key cannot. Examples applicable to this Recommendation include: 1. The computation of a keyed-hash message authentication code. 2. The verification of a keyed-hash message authentication code. 3. The generation of a digital signature on a message. 4. The verification of a digital signature.
Source(s):
NIST SP 800-107 Rev. 1 under Key

  A  binary  string  used  as  a  secret  parameter  by  a  cryptographic algorithm. In this Recommendation, a cryptographic key shall be either a truly random binary string of a length specified by the cryptographic algorithm or a pseudorandom binary string of the specified length that is computationally indistinguishable from one selected uniformly at random from the set of all binary strings of that length.
Source(s):
NIST SP 800-108 under Cryptographic key

  A cryptographic key that can be directly used by a cryptographic algorithm to perform a cryptographic operation.
Source(s):
NIST SP 800-152 under Key (plaintext)

  A parameter that determines the transformation from plaintext to ciphertext and vice versa. (A DEA key is a 64-bit parameter consisting of 56 independent bits and 8 parity bits). Multiple (1, 2 or 3) keys may be used in the Triple Data Encryption Algorithm.
Source(s):
NIST SP 800-20 under Cryptographic key

  A parameter used in the block cipher algorithm that determines the forward cipher operation and the inverse cipher operation.
Source(s):
NIST SP 800-38A under Cryptographic Key

  The parameter of the block cipher that determines the selection of the forward cipher function from the family of permutations.
Source(s):
NIST SP 800-38B under Key (Block Cipher Key)
NIST SP 800-38D under Key

  A parameter used in the block cipher algorithm that determines the forward cipher function.
Source(s):
NIST SP 800-38C under Cryptographic Key

  A value used to control cryptographic operations, such as decryption, encryption, signature generation, or signature verification. For the purposes of these guidelines, key requirements shall meet the minimum requirements stated in Table 2 of NIST SP 800-57 Part 1. See also Asymmetric Keys, Symmetric Key.
Source(s):
NIST SP 800-63-3 under Cryptographic Key

  A parameter that determines the transformation using DEA and TDEA forward and inverse operations.
Source(s):
NIST SP 800-67 Rev. 2 under Cryptographic Key

  A parameter used in conjunction with a cryptographic algorithm that determines its operation in such a way that an entity with knowledge of the key can reproduce the operation, while an entity without knowledge of the key cannot. Examples of the use of a key that are applicable to this Recommendation include: 1. The computation of a digital signature from data, and 2. The verification of a digital signature.
Source(s):
NIST SP 800-89 under Key

  See cryptographic key.
Source(s):
NIST SP 800-133 Rev. 2 under Key
NIST SP 800-175B Rev. 1 under Key
NIST SP 800-20 under Key
NIST SP 800-57 Part 1 Rev. 5 under Key
NIST SP 800-67 Rev. 2 under Key
NIST SP 800-90A Rev. 1 under Key

  A value used to control cryptographic operations, such as decryption, encryption, signature generation, or signature verification. For the purposes of these guidelines, key requirements shall meet the minimum requirements stated in Table 2 of NIST SP 800-57 Part 1. See also Asymmetric Keys, Symmetric Key.
Source(s):
NIST SP 800-63-3 under Cryptographic Key

  A parameter used in conjunction with a cryptographic algorithm that determines its operation in such a way that an entity with knowledge of the key can reproduce or reverse the operation while an entity without knowledge of the key cannot. Examples include 1. The transformation of plaintext data into ciphertext data, 2. The transformation of ciphertext data into plaintext data, 3. The computation of a digital signature from data, 4. The verification of a digital signature, 5. The computation of a message authentication code (MAC) from data, 6. The verification of a MAC received with data, 7. The computation of a shared secret that is used to derive keying material.
Source(s):
NIST SP 800-175B Rev. 1 under Cryptographic key

  A value used to control cryptographic operations, such as decryption, encryption, signature generation, or signature verification.
Source(s):
NIST SP 1800-21B under Cryptographic Key from NIST SP 800-63-3

  A cryptographic key. In this document, keys generally refer to public key cryptography key pairs used for authentication of users and/or machines (using digital signatures). Examples include identity key and authorized keys. The SSH protocol also uses host keys that are used for authenticating SSH servers to SSH clients connecting them.
Source(s):
NISTIR 7966 under Key