Key derivation refers to how a device or piece of software constructs cryptographic keys from other keys and variables, including passwords (so called password-based key derivation). NIST SP800-108 asserts a Key Derivation Function (KDF) is a function with which an input key and other input data are used to generate (that is, derive) keying material that can be employed by cryptographic algorithms. Source: http://csrc.nist.gov/publications/nistpubs/800-108/sp800-108.pdf.
A generalized depiction of key derivation is shown in the following screenshot:
KDF.graffle
Poor practices in key derivation led to the US Government disallowing ...
