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See symmetric (secret key) algorithm.
NIST SP 800-175B Rev. 1 under Secret-key (symmetric) cryptographic algorithm
A cryptographic algorithm that uses the same secret key for an operation and its complement (e.g., encryption and decryption). The key is kept secret and is called either a secret key or symmetric key.
NIST SP 800-175B Rev. 1 under Symmetric-key (secret-key) algorithm
See Symmetric-key algorithm.
NIST SP 800-57 Part 1 Rev. 5 under Secret-key algorithm
A cryptographic algorithm that uses a single key (i.e., a secret key) for both encryption and decryption.
[Superseded] from FIPS 140-2 - Adapted