# 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 abc

import six


@six.add_metaclass(abc.ABCMeta)
class KeyDerivationFunction(object):
    @abc.abstractmethod
    def derive(self, key_material):
        """
        Deterministically generates and returns a new key based on the existing
        key material.
        """

    @abc.abstractmethod
    def verify(self, key_material, expected_key):
        """
        Checks whether the key generated by the key material matches the
        expected derived key. Raises an exception if they do not match.
        """