Pbkdf_two

pbkdf_two

import hmac
import struct
 
def pbkdf2(password, salt, iters, keylen, digestmod):
    """Run the PBKDF2 (Password-Based Key Derivation Function 2) algorithm
    and return the derived key. The arguments are:
 
    password (bytes or bytearray) -- the input password
    salt (bytes or bytearray) -- a cryptographic salt
    iters (int) -- number of iterations
    keylen (int) -- length of key to derive
    digestmod -- a cryptographic hash function: either a module
        supporting PEP 247, a hashlib constructor, or (in Python 3.4
        or later) the name of a hash function.
 
    For example:
 
    >>> import hashlib
    >>> from binascii import hexlify, unhexlify
    >>> password = b'Squeamish Ossifrage'
    >>> salt = unhexlify(b'1234567878563412')
    >>> hexlify(pbkdf2(password, salt, 500, 16, hashlib.sha1))
    b'9e8f1072bdf5ef042bd988c7da83e43b'
 
    """
    h = hmac.new(password, digestmod=digestmod)
    def prf(data):
        hm = h.copy()
        hm.update(data)
        return bytearray(hm.digest())
 
    key = bytearray()
    i = 1
    while len(key) < keylen:
        T = U = prf(salt + struct.pack('>i', i))
        for _ in range(iters - 1):
            U = prf(U)
            T = bytearray(x ^ y for x, y in zip(T, U))
        key += T
        i += 1
 
    return key[:keylen]