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# ===================================================================
#
# Copyright (c) 2021, Legrandin <helderijs@gmail.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
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#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# ===================================================================
from Crypto.Util.py3compat import bord, is_bytes, tobytes
from . import cSHAKE128
from .cSHAKE128 import _encode_str, _right_encode
class TupleHash(object):
"""A Tuple hash object.
Do not instantiate directly.
Use the :func:`new` function.
"""
def __init__(self, custom, cshake, digest_size):
self.digest_size = digest_size
self._cshake = cshake._new(b'', custom, b'TupleHash')
self._digest = None
def update(self, data):
"""Authenticate the next byte string in the tuple.
Args:
data (bytes/bytearray/memoryview): The next byte string.
"""
if self._digest is not None:
raise TypeError("You cannot call 'update' after 'digest' or 'hexdigest'")
if not is_bytes(data):
raise TypeError("You can only call 'update' on bytes")
self._cshake.update(_encode_str(tobytes(data)))
return self
def digest(self):
"""Return the **binary** (non-printable) digest of the tuple of byte strings.
:return: The hash digest. Binary form.
:rtype: byte string
"""
if self._digest is None:
self._cshake.update(_right_encode(self.digest_size * 8))
self._digest = self._cshake.read(self.digest_size)
return self._digest
def hexdigest(self):
"""Return the **printable** digest of the tuple of byte strings.
:return: The hash digest. Hexadecimal encoded.
:rtype: string
"""
return "".join(["%02x" % bord(x) for x in tuple(self.digest())])
def new(self, **kwargs):
"""Return a new instance of a TupleHash object.
See :func:`new`.
"""
if "digest_bytes" not in kwargs and "digest_bits" not in kwargs:
kwargs["digest_bytes"] = self.digest_size
return new(**kwargs)
def new(**kwargs):
"""Create a new TupleHash128 object.
Args:
digest_bytes (integer):
Optional. The size of the digest, in bytes.
Default is 64. Minimum is 8.
digest_bits (integer):
Optional and alternative to ``digest_bytes``.
The size of the digest, in bits (and in steps of 8).
Default is 512. Minimum is 64.
custom (bytes):
Optional.
A customization bytestring (``S`` in SP 800-185).
:Return: A :class:`TupleHash` object
"""
digest_bytes = kwargs.pop("digest_bytes", None)
digest_bits = kwargs.pop("digest_bits", None)
if None not in (digest_bytes, digest_bits):
raise TypeError("Only one digest parameter must be provided")
if (None, None) == (digest_bytes, digest_bits):
digest_bytes = 64
if digest_bytes is not None:
if digest_bytes < 8:
raise ValueError("'digest_bytes' must be at least 8")
else:
if digest_bits < 64 or digest_bits % 8:
raise ValueError("'digest_bytes' must be at least 64 "
"in steps of 8")
digest_bytes = digest_bits // 8
custom = kwargs.pop("custom", b'')
if kwargs:
raise TypeError("Unknown parameters: " + str(kwargs))
return TupleHash(custom, cSHAKE128, digest_bytes)
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