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venv/Lib/site-packages/cryptography/hazmat/primitives/_cipheralgorithm.py

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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