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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import, division, print_function
from enum import Enum
class _Operation(Enum):
encrypt = 0
decrypt = 1
class BlockCipher(object):
def __init__(self, cipher, mode, api=None):
super(BlockCipher, self).__init__()
if api is None:
from cryptography.bindings import _default_api as api
self.cipher = cipher
self.mode = mode
self._api = api
self._ctx = api.create_block_cipher_context(cipher, mode)
self._operation = None
def encrypt(self, plaintext):
if self._ctx is None:
raise ValueError("BlockCipher was already finalized")
if self._operation is None:
self._operation = _Operation.encrypt
elif self._operation is not _Operation.encrypt:
raise ValueError("BlockCipher cannot encrypt when the operation is"
" set to %s" % self._operation.name)
return self._api.update_encrypt_context(self._ctx, plaintext)
def finalize(self):
if self._ctx is None:
raise ValueError("BlockCipher was already finalized")
if self._operation is _Operation.encrypt:
result = self._api.finalize_encrypt_context(self._ctx)
else:
raise ValueError("BlockCipher cannot finalize the unknown "
"operation %s" % self._operation.name)
self._ctx = None
return result
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