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Editing: cSHAKE128.py
# =================================================================== # # 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 # are met: # # 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. # # 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 # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE # POSSIBILITY OF SUCH DAMAGE. # =================================================================== from Crypto.Util.py3compat import bchr from Crypto.Util._raw_api import (VoidPointer, SmartPointer, create_string_buffer, get_raw_buffer, c_size_t, c_uint8_ptr, c_ubyte) from Crypto.Util.number import long_to_bytes from Crypto.Hash.keccak import _raw_keccak_lib def _left_encode(x): """Left encode function as defined in NIST SP 800-185""" assert (x < (1 << 2040) and x >= 0) # Get number of bytes needed to represent this integer. num = 1 if x == 0 else (x.bit_length() + 7) // 8 return bchr(num) + long_to_bytes(x) def _right_encode(x): """Right encode function as defined in NIST SP 800-185""" assert (x < (1 << 2040) and x >= 0) # Get number of bytes needed to represent this integer. num = 1 if x == 0 else (x.bit_length() + 7) // 8 return long_to_bytes(x) + bchr(num) def _encode_str(x): """Encode string function as defined in NIST SP 800-185""" bitlen = len(x) * 8 if bitlen >= (1 << 2040): raise ValueError("String too large to encode in cSHAKE") return _left_encode(bitlen) + x def _bytepad(x, length): """Zero pad byte string as defined in NIST SP 800-185""" to_pad = _left_encode(length) + x # Note: this implementation works with byte aligned strings, # hence no additional bit padding is needed at this point. npad = (length - len(to_pad) % length) % length return to_pad + b'\x00' * npad class cSHAKE_XOF(object): """A cSHAKE hash object. Do not instantiate directly. Use the :func:`new` function. """ def __init__(self, data, custom, capacity, function): state = VoidPointer() if custom or function: prefix_unpad = _encode_str(function) + _encode_str(custom) prefix = _bytepad(prefix_unpad, (1600 - capacity)//8) self._padding = 0x04 else: prefix = None self._padding = 0x1F # for SHAKE result = _raw_keccak_lib.keccak_init(state.address_of(), c_size_t(capacity//8), c_ubyte(24)) if result: raise ValueError("Error %d while instantiating cSHAKE" % result) self._state = SmartPointer(state.get(), _raw_keccak_lib.keccak_destroy) self._is_squeezing = False if prefix: self.update(prefix) if data: self.update(data) def update(self, data): """Continue hashing of a message by consuming the next chunk of data. Args: data (byte string/byte array/memoryview): The next chunk of the message being hashed. """ if self._is_squeezing: raise TypeError("You cannot call 'update' after the first 'read'") result = _raw_keccak_lib.keccak_absorb(self._state.get(), c_uint8_ptr(data), c_size_t(len(data))) if result: raise ValueError("Error %d while updating %s state" % (result, self.name)) return self def read(self, length): """ Compute the next piece of XOF output. .. note:: You cannot use :meth:`update` anymore after the first call to :meth:`read`. Args: length (integer): the amount of bytes this method must return :return: the next piece of XOF output (of the given length) :rtype: byte string """ self._is_squeezing = True bfr = create_string_buffer(length) result = _raw_keccak_lib.keccak_squeeze(self._state.get(), bfr, c_size_t(length), c_ubyte(self._padding)) if result: raise ValueError("Error %d while extracting from %s" % (result, self.name)) return get_raw_buffer(bfr) def _new(data, custom, function): # Use Keccak[256] return cSHAKE_XOF(data, custom, 256, function) def new(data=None, custom=None): """Return a fresh instance of a cSHAKE128 object. Args: data (bytes/bytearray/memoryview): Optional. The very first chunk of the message to hash. It is equivalent to an early call to :meth:`update`. custom (bytes): Optional. A customization bytestring (``S`` in SP 800-185). :Return: A :class:`cSHAKE_XOF` object """ # Use Keccak[256] return cSHAKE_XOF(data, custom, 256, b'')
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