91 lines
2.5 KiB
Python
91 lines
2.5 KiB
Python
#!/usr/bin/env python3
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import sys; assert sys.version_info[0] >= 3, "Python 3 required."
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from pyblake2 import blake2s
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from sapling_jubjub import Point, JUBJUB_COFACTOR
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from tv_output import render_args, render_tv
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from utils import i2leosp
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# First 64 bytes of the BLAKE2s input during group hash.
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# This is chosen to be some random string that we couldn't have
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# anticipated when we designed the algorithm, for rigidity purposes.
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# We deliberately use an ASCII hex string of 32 bytes here.
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URS = b'096b36a5804bfacef1691e173c366a47ff5ba84a44f26ddd7e8d9f79d5b42df0'
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#
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# Group hash
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#
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def group_hash(D, M):
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digest = blake2s(person=D)
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digest.update(URS)
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digest.update(M)
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p = Point.from_bytes(digest.digest())
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if p is None:
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return None
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q = p * JUBJUB_COFACTOR
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if q == Point.ZERO:
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return None
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return q
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def find_group_hash(D, M):
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i = 0
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while True:
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p = group_hash(D, M + bytes([i]))
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if p is not None:
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return p
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i += 1
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assert i < 256
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#
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# Sapling generators
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#
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SPENDING_KEY_BASE = find_group_hash(b'Zcash_G_', b'')
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PROVING_KEY_BASE = find_group_hash(b'Zcash_H_', b'')
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NOTE_POSITION_BASE = find_group_hash(b'Zcash_J_', b'')
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WINDOWED_PEDERSEN_RANDOMNESS_BASE = find_group_hash(b'Zcash_PH', b'r')
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VALUE_COMMITMENT_VALUE_BASE = find_group_hash(b'Zcash_cv', b'v')
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VALUE_COMMITMENT_RANDOMNESS_BASE = find_group_hash(b'Zcash_cv', b'r')
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required_bases = 4
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PEDERSEN_BASES = [find_group_hash(b'Zcash_PH', i2leosp(32, iminus1))
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for iminus1 in range(0, required_bases)]
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def main():
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render_tv(
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render_args(),
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'sapling_generators',
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(
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('skb', '[u8; 32]'),
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('pkb', '[u8; 32]'),
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('npb', '[u8; 32]'),
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('wprb', '[u8; 32]'),
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('vcvb', '[u8; 32]'),
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('vcrb', '[u8; 32]'),
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('pb0', '[u8; 32]'),
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('pb1', '[u8; 32]'),
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('pb2', '[u8; 32]'),
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('pb3', '[u8; 32]'),
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),
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{
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'skb': bytes(SPENDING_KEY_BASE),
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'pkb': bytes(PROVING_KEY_BASE),
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'npb': bytes(NOTE_POSITION_BASE),
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'wprb': bytes(WINDOWED_PEDERSEN_RANDOMNESS_BASE),
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'vcvb': bytes(VALUE_COMMITMENT_VALUE_BASE),
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'vcrb': bytes(VALUE_COMMITMENT_RANDOMNESS_BASE),
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'pb0': bytes(PEDERSEN_BASES[0]),
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'pb1': bytes(PEDERSEN_BASES[1]),
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'pb2': bytes(PEDERSEN_BASES[2]),
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'pb3': bytes(PEDERSEN_BASES[3]),
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},
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)
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if __name__ == '__main__':
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main()
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