A key-derivation function or other approved procedure for deriving keying material.
NIST SP 800-133 Rev. 2
NIST SP 800-57 Part 1 Rev. 5
As used in this Recommendation, a method by which secret keying material is derived from a shared secret and other information. A key-derivation method may use a key-derivation function or a key-derivation procedure.
NIST SP 800-56B Rev. 2
As used in this Recommendation, a process that derives secret keying material from a shared secret. This Recommendation specifies both one-step and two-step key-derivation methods.
NIST SP 800-56C Rev. 2