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56 lines
2.1 KiB
Python
56 lines
2.1 KiB
Python
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# Copyright (c) 2020 Pieter Wuille
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# Distributed under the MIT software license, see the accompanying
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# file COPYING or http://www.opensource.org/licenses/mit-license.php.
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"""Native Python MuHash3072 implementation."""
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import hashlib
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import unittest
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from .chacha20 import chacha20_block
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def data_to_num3072(data):
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"""Hash a 32-byte array data to a 3072-bit number using 6 Chacha20 operations."""
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bytes384 = b""
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for counter in range(6):
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bytes384 += chacha20_block(data, bytes(12), counter)
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return int.from_bytes(bytes384, 'little')
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class MuHash3072:
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"""Class representing the MuHash3072 computation of a set.
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See https://cseweb.ucsd.edu/~mihir/papers/inchash.pdf and https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-May/014337.html
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"""
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MODULUS = 2**3072 - 1103717
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def __init__(self):
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"""Initialize for an empty set."""
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self.numerator = 1
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self.denominator = 1
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def insert(self, data):
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"""Insert a byte array data in the set."""
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data_hash = hashlib.sha256(data).digest()
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self.numerator = (self.numerator * data_to_num3072(data_hash)) % self.MODULUS
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def remove(self, data):
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"""Remove a byte array from the set."""
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data_hash = hashlib.sha256(data).digest()
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self.denominator = (self.denominator * data_to_num3072(data_hash)) % self.MODULUS
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def digest(self):
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"""Extract the final hash. Does not modify this object."""
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val = (self.numerator * pow(self.denominator, -1, self.MODULUS)) % self.MODULUS
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bytes384 = val.to_bytes(384, 'little')
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return hashlib.sha256(bytes384).digest()
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class TestFrameworkMuhash(unittest.TestCase):
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def test_muhash(self):
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muhash = MuHash3072()
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muhash.insert(b'\x00' * 32)
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muhash.insert((b'\x01' + b'\x00' * 31))
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muhash.remove((b'\x02' + b'\x00' * 31))
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finalized = muhash.digest()
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# This mirrors the result in the C++ MuHash3072 unit test
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self.assertEqual(finalized[::-1].hex(), "10d312b100cbd32ada024a6646e40d3482fcff103668d2625f10002a607d5863")
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