Erlang based HMAC-based Extract-and-Expand Key Derivation Function (HKDF)

See RFC 5869 for details. This is a very straigth forward implementation, including the tests from RFC5869 as eunit tests. It supports the hash functions md5, sha, sha224, sha256, sha384, sha512.

Usage

• Hash = md5 | sha | sha224 | sha256 | sha384 | sha512.
• IKM = input keying material.
• salt = optional salt value (a non-secret random value)

PKR = hkdf:extract(Hash, IKM).

or

PKR = hkdf:extract(Hash, IKM, Salt).

Next, expand the PKR to the required length

• info = optional context and application specific information,
• L = length of output keying material in octets.

OKM = expand(Hash, PRK, Info, L)