Source code for cryptography.hazmat.primitives.kdf.pbkdf2

# 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

from cryptography import utils
from cryptography.exceptions import (
    AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.backends.interfaces import PBKDF2HMACBackend
from cryptography.hazmat.primitives import constant_time
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction

[docs]@utils.register_interface(KeyDerivationFunction) class PBKDF2HMAC(object): def __init__(self, algorithm, length, salt, iterations, backend): if not isinstance(backend, PBKDF2HMACBackend): raise UnsupportedAlgorithm( "Backend object does not implement PBKDF2HMACBackend.", _Reasons.BACKEND_MISSING_INTERFACE ) if not backend.pbkdf2_hmac_supported(algorithm): raise UnsupportedAlgorithm( "{0} is not supported for PBKDF2 by this backend.".format(, _Reasons.UNSUPPORTED_HASH ) self._used = False self._algorithm = algorithm self._length = length utils._check_bytes("salt", salt) self._salt = salt self._iterations = iterations self._backend = backend
[docs] def derive(self, key_material): if self._used: raise AlreadyFinalized("PBKDF2 instances can only be used once.") self._used = True utils._check_byteslike("key_material", key_material) return self._backend.derive_pbkdf2_hmac( self._algorithm, self._length, self._salt, self._iterations, key_material )
[docs] def verify(self, key_material, expected_key): derived_key = self.derive(key_material) if not constant_time.bytes_eq(derived_key, expected_key): raise InvalidKey("Keys do not match.")