Module hkdf 

HMAC (Hash-based Message Authentication Code)

Functions

derive_key

One-shot HKDF: extract-then-expand in a single call.

expand

HKDF expand step: OKM = T(1) || T(2) || ..., where T(i) = HMAC-Hash(PRK, T(i-1) || info || i).

extract

HKDF extract step: PRK = HMAC-Hash(salt, IKM).