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122 lines
4.1 KiB
122 lines
4.1 KiB
#!/usr/bin/env python3
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# Copyright (c) 2017 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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"""Reference implementation for Bech32 and segwit addresses."""
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import unittest
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CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
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def bech32_polymod(values):
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"""Internal function that computes the Bech32 checksum."""
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generator = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3]
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chk = 1
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for value in values:
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top = chk >> 25
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chk = (chk & 0x1ffffff) << 5 ^ value
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for i in range(5):
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chk ^= generator[i] if ((top >> i) & 1) else 0
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return chk
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def bech32_hrp_expand(hrp):
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"""Expand the HRP into values for checksum computation."""
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return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp]
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def bech32_verify_checksum(hrp, data):
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"""Verify a checksum given HRP and converted data characters."""
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return bech32_polymod(bech32_hrp_expand(hrp) + data) == 1
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def bech32_create_checksum(hrp, data):
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"""Compute the checksum values given HRP and data."""
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values = bech32_hrp_expand(hrp) + data
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polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ 1
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return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)]
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def bech32_encode(hrp, data):
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"""Compute a Bech32 string given HRP and data values."""
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combined = data + bech32_create_checksum(hrp, data)
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return hrp + '1' + ''.join([CHARSET[d] for d in combined])
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def bech32_decode(bech):
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"""Validate a Bech32 string, and determine HRP and data."""
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if ((any(ord(x) < 33 or ord(x) > 126 for x in bech)) or
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(bech.lower() != bech and bech.upper() != bech)):
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return (None, None)
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bech = bech.lower()
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pos = bech.rfind('1')
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if pos < 1 or pos + 7 > len(bech) or len(bech) > 90:
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return (None, None)
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if not all(x in CHARSET for x in bech[pos+1:]):
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return (None, None)
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hrp = bech[:pos]
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data = [CHARSET.find(x) for x in bech[pos+1:]]
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if not bech32_verify_checksum(hrp, data):
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return (None, None)
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return (hrp, data[:-6])
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def convertbits(data, frombits, tobits, pad=True):
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"""General power-of-2 base conversion."""
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acc = 0
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bits = 0
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ret = []
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maxv = (1 << tobits) - 1
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max_acc = (1 << (frombits + tobits - 1)) - 1
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for value in data:
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if value < 0 or (value >> frombits):
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return None
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acc = ((acc << frombits) | value) & max_acc
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bits += frombits
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while bits >= tobits:
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bits -= tobits
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ret.append((acc >> bits) & maxv)
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if pad:
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if bits:
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ret.append((acc << (tobits - bits)) & maxv)
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elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
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return None
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return ret
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def decode_segwit_address(hrp, addr):
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"""Decode a segwit address."""
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hrpgot, data = bech32_decode(addr)
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if hrpgot != hrp:
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return (None, None)
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decoded = convertbits(data[1:], 5, 8, False)
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if decoded is None or len(decoded) < 2 or len(decoded) > 40:
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return (None, None)
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if data[0] > 16:
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return (None, None)
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if data[0] == 0 and len(decoded) != 20 and len(decoded) != 32:
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return (None, None)
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return (data[0], decoded)
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def encode_segwit_address(hrp, witver, witprog):
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"""Encode a segwit address."""
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ret = bech32_encode(hrp, [witver] + convertbits(witprog, 8, 5))
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if decode_segwit_address(hrp, ret) == (None, None):
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return None
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return ret
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class TestFrameworkScript(unittest.TestCase):
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def test_segwit_encode_decode(self):
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def test_python_bech32(addr):
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hrp = addr[:4]
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self.assertEqual(hrp, "bcrt")
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(witver, witprog) = decode_segwit_address(hrp, addr)
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self.assertEqual(encode_segwit_address(hrp, witver, witprog), addr)
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# P2WPKH
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test_python_bech32('bcrt1qthmht0k2qnh3wy7336z05lu2km7emzfpm3wg46')
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# P2WSH
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test_python_bech32('bcrt1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq3xueyj')
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test_python_bech32('bcrt1qft5p2uhsdcdc3l2ua4ap5qqfg4pjaqlp250x7us7a8qqhrxrxfsqseac85')
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