# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

import binascii

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.hkdf import HKDF

IKM = binascii.unhexlify(b"0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b")
L = 1200
OKM = HKDF(
    algorithm=hashes.SHA256(), length=L, salt=None, info=None,
    backend=default_backend()
).derive(IKM)


def _build_vectors():
    output = []
    output.append("COUNT = 0")
    output.append("Hash = SHA-256")
    output.append("IKM = " + binascii.hexlify(IKM).decode("ascii"))
    output.append("salt = ")
    output.append("info = ")
    output.append("L = {}".format(L))
    output.append("OKM = " + binascii.hexlify(OKM).decode("ascii"))
    return "\n".join(output)


def _write_file(data, filename):
    with open(filename, 'w') as f:
        f.write(data)


if __name__ == '__main__':
    _write_file(_build_vectors(), 'hkdf.txt')