http://www.rfc-editor.org/rfc/rfc5869.txt
RFC 5869: HMAC-based Extract-and-Expand Key Derivation Function (HKDF), H. Krawczyk, P. Eronen2010-05-01T23:00:00-00:00This document specifies a simple Hashed Message Authentication Code (HMAC)-based key derivation function (HKDF), which can be used as a building block in various protocols and applications. The key derivation function (KDF) is intended to support a wide range of applications and requirements, and is conservative in its use of cryptographic hash functions. This document is not an Internet Standards Track specification; it is published for informational purposes.