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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.hazmat._der import (
DERReader, INTEGER, SEQUENCE, encode_der, encode_der_integer
)
from cryptography.hazmat.primitives import hashes
def decode_dss_signature(signature):
with DERReader(signature).read_single_element(SEQUENCE) as seq:
r = seq.read_element(INTEGER).as_integer()
s = seq.read_element(INTEGER).as_integer()
return r, s
def encode_dss_signature(r, s):
return encode_der(
SEQUENCE,
encode_der(INTEGER, encode_der_integer(r)),
encode_der(INTEGER, encode_der_integer(s)),
)
class Prehashed(object):
def __init__(self, algorithm):
if not isinstance(algorithm, hashes.HashAlgorithm):
raise TypeError("Expected instance of HashAlgorithm.")
self._algorithm = algorithm
self._digest_size = algorithm.digest_size
digest_size = utils.read_only_property("_digest_size")
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