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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 absolute_import, division, print_function
from cryptography import utils
from cryptography.exceptions import (
AlreadyFinalized, UnsupportedAlgorithm, _Reasons
)
class Poly1305(object):
def __init__(self, key):
from cryptography.hazmat.backends.openssl.backend import backend
if not backend.poly1305_supported():
raise UnsupportedAlgorithm(
"poly1305 is not supported by this version of OpenSSL.",
_Reasons.UNSUPPORTED_MAC
)
self._ctx = backend.create_poly1305_ctx(key)
def update(self, data):
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
utils._check_byteslike("data", data)
self._ctx.update(data)
def finalize(self):
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
mac = self._ctx.finalize()
self._ctx = None
return mac
def verify(self, tag):
utils._check_bytes("tag", tag)
if self._ctx is None:
raise AlreadyFinalized("Context was already finalized.")
ctx, self._ctx = self._ctx, None
ctx.verify(tag)
@classmethod
def generate_tag(cls, key, data):
p = Poly1305(key)
p.update(data)
return p.finalize()
@classmethod
def verify_tag(cls, key, data, tag):
p = Poly1305(key)
p.update(data)
p.verify(tag)
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