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# 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 annotations
import abc
from cryptography import utils
# This exists to break an import cycle. It is normally accessible from the
# ciphers module.
class CipherAlgorithm(metaclass=abc.ABCMeta):
@property
@abc.abstractmethod
def name(self) -> str:
"""
A string naming this mode (e.g. "AES", "Camellia").
"""
@property
@abc.abstractmethod
def key_sizes(self) -> frozenset[int]:
"""
Valid key sizes for this algorithm in bits
"""
@property
@abc.abstractmethod
def key_size(self) -> int:
"""
The size of the key being used as an integer in bits (e.g. 128, 256).
"""
class BlockCipherAlgorithm(CipherAlgorithm):
key: bytes
@property
@abc.abstractmethod
def block_size(self) -> int:
"""
The size of a block as an integer in bits (e.g. 64, 128).
"""
def _verify_key_size(algorithm: CipherAlgorithm, key: bytes) -> bytes:
# Verify that the key is instance of bytes
utils._check_byteslike("key", key)
# Verify that the key size matches the expected key size
if len(key) * 8 not in algorithm.key_sizes:
raise ValueError(
f"Invalid key size ({len(key) * 8}) for {algorithm.name}."
)
return key
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