Janus
7 years ago
committed by
ThomasV
ThomasV
3 changed files with 5 additions and 128 deletions
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# Copyright (c) 2017 Pieter Wuille |
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# |
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# Permission is hereby granted, free of charge, to any person obtaining a copy |
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# of this software and associated documentation files (the "Software"), to deal |
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# in the Software without restriction, including without limitation the rights |
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
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# copies of the Software, and to permit persons to whom the Software is |
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# furnished to do so, subject to the following conditions: |
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# |
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# The above copyright notice and this permission notice shall be included in |
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# all copies or substantial portions of the Software. |
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# |
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
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# THE SOFTWARE. |
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"""Reference implementation for Bech32 and segwit addresses.""" |
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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(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(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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assert decode(hrp, ret) is not (None, None) |
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return ret |
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