# 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)