def pbkdf2(password, salt, iterations, dklen=0, digest=None):
    """
    Implements PBKDF2 as defined in RFC 2898, section 5.2

    HMAC+SHA256 is used as the default pseudo random function.

    As of 2011, 10,000 iterations was the recommended default which
    took 100ms on a 2.2Ghz Core 2 Duo. This is probably the bare
    minimum for security given 1000 iterations was recommended in
    2001. This code is very well optimized for CPython and is only
    four times slower than openssl's implementation. Look in
    django.contrib.auth.hashers for the present default.
    """
    assert iterations > 0
    if not digest:
        digest = hashlib.sha256
    password = force_bytes(password)
    salt = force_bytes(salt)
    hlen = digest().digest_size
    if not dklen:
        dklen = hlen
    if dklen > (2 ** 32 - 1) * hlen:
        raise OverflowError('dklen too big')
    l = -(-dklen // hlen)
    r = dklen - (l - 1) * hlen

    hex_format_string = "%%0%ix" % (hlen * 2)

    inner, outer = digest(), digest()
    if len(password) > inner.block_size:
        password = digest(password).digest()
    password += b'\x00' * (inner.block_size - len(password))
    inner.update(password.translate(hmac.trans_36))
    outer.update(password.translate(hmac.trans_5C))

    def F(i):
        def U():
            u = salt + struct.pack(b'>I', i)
            for j in xrange(int(iterations)):
                dig1, dig2 = inner.copy(), outer.copy()
                dig1.update(u)
                dig2.update(dig1.digest())
                u = dig2.digest()
                yield _bin_to_long(u)
        return _long_to_bin(reduce(operator.xor, U()), hex_format_string)

    T = [F(x) for x in range(1, l + 1)]
    return b''.join(T[:-1]) + T[-1][:r]
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/utils/crypto.py/pbkdf2/original