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1# This file is dual licensed under the terms of the Apache License, Version
2# 2.0, and the BSD License. See the LICENSE file in the root of this repository
3# for complete details.
5from __future__ import annotations
7import abc
9from cryptography import utils
11# This exists to break an import cycle. It is normally accessible from the
12# ciphers module.
15class CipherAlgorithm(metaclass=abc.ABCMeta):
16 @property
17 @abc.abstractmethod
18 def name(self) -> str:
19 """
20 A string naming this mode (e.g. "AES", "Camellia").
21 """
23 @property
24 @abc.abstractmethod
25 def key_sizes(self) -> frozenset[int]:
26 """
27 Valid key sizes for this algorithm in bits
28 """
30 @property
31 @abc.abstractmethod
32 def key_size(self) -> int:
33 """
34 The size of the key being used as an integer in bits (e.g. 128, 256).
35 """
38class BlockCipherAlgorithm(CipherAlgorithm):
39 key: utils.Buffer
41 @property
42 @abc.abstractmethod
43 def block_size(self) -> int:
44 """
45 The size of a block as an integer in bits (e.g. 64, 128).
46 """
49def _verify_key_size(
50 algorithm: CipherAlgorithm, key: utils.Buffer
51) -> utils.Buffer:
52 # Verify that the key is instance of bytes
53 utils._check_byteslike("key", key)
55 # Verify that the key size matches the expected key size
56 if len(key) * 8 not in algorithm.key_sizes:
57 raise ValueError(
58 f"Invalid key size ({len(key) * 8}) for {algorithm.name}."
59 )
60 return key