You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
107 lines
3.4 KiB
107 lines
3.4 KiB
#!/usr/bin/env python3 |
|
# Copyright (c) 2017 Pieter Wuille |
|
# Distributed under the MIT software license, see the accompanying |
|
# file COPYING or http://www.opensource.org/licenses/mit-license.php. |
|
"""Reference implementation for Bech32 and segwit addresses.""" |
|
|
|
|
|
CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l" |
|
|
|
|
|
def bech32_polymod(values): |
|
"""Internal function that computes the Bech32 checksum.""" |
|
generator = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3] |
|
chk = 1 |
|
for value in values: |
|
top = chk >> 25 |
|
chk = (chk & 0x1ffffff) << 5 ^ value |
|
for i in range(5): |
|
chk ^= generator[i] if ((top >> i) & 1) else 0 |
|
return chk |
|
|
|
|
|
def bech32_hrp_expand(hrp): |
|
"""Expand the HRP into values for checksum computation.""" |
|
return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp] |
|
|
|
|
|
def bech32_verify_checksum(hrp, data): |
|
"""Verify a checksum given HRP and converted data characters.""" |
|
return bech32_polymod(bech32_hrp_expand(hrp) + data) == 1 |
|
|
|
|
|
def bech32_create_checksum(hrp, data): |
|
"""Compute the checksum values given HRP and data.""" |
|
values = bech32_hrp_expand(hrp) + data |
|
polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ 1 |
|
return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)] |
|
|
|
|
|
def bech32_encode(hrp, data): |
|
"""Compute a Bech32 string given HRP and data values.""" |
|
combined = data + bech32_create_checksum(hrp, data) |
|
return hrp + '1' + ''.join([CHARSET[d] for d in combined]) |
|
|
|
|
|
def bech32_decode(bech): |
|
"""Validate a Bech32 string, and determine HRP and data.""" |
|
if ((any(ord(x) < 33 or ord(x) > 126 for x in bech)) or |
|
(bech.lower() != bech and bech.upper() != bech)): |
|
return (None, None) |
|
bech = bech.lower() |
|
pos = bech.rfind('1') |
|
if pos < 1 or pos + 7 > len(bech) or len(bech) > 90: |
|
return (None, None) |
|
if not all(x in CHARSET for x in bech[pos+1:]): |
|
return (None, None) |
|
hrp = bech[:pos] |
|
data = [CHARSET.find(x) for x in bech[pos+1:]] |
|
if not bech32_verify_checksum(hrp, data): |
|
return (None, None) |
|
return (hrp, data[:-6]) |
|
|
|
|
|
def convertbits(data, frombits, tobits, pad=True): |
|
"""General power-of-2 base conversion.""" |
|
acc = 0 |
|
bits = 0 |
|
ret = [] |
|
maxv = (1 << tobits) - 1 |
|
max_acc = (1 << (frombits + tobits - 1)) - 1 |
|
for value in data: |
|
if value < 0 or (value >> frombits): |
|
return None |
|
acc = ((acc << frombits) | value) & max_acc |
|
bits += frombits |
|
while bits >= tobits: |
|
bits -= tobits |
|
ret.append((acc >> bits) & maxv) |
|
if pad: |
|
if bits: |
|
ret.append((acc << (tobits - bits)) & maxv) |
|
elif bits >= frombits or ((acc << (tobits - bits)) & maxv): |
|
return None |
|
return ret |
|
|
|
|
|
def decode(hrp, addr): |
|
"""Decode a segwit address.""" |
|
hrpgot, data = bech32_decode(addr) |
|
if hrpgot != hrp: |
|
return (None, None) |
|
decoded = convertbits(data[1:], 5, 8, False) |
|
if decoded is None or len(decoded) < 2 or len(decoded) > 40: |
|
return (None, None) |
|
if data[0] > 16: |
|
return (None, None) |
|
if data[0] == 0 and len(decoded) != 20 and len(decoded) != 32: |
|
return (None, None) |
|
return (data[0], decoded) |
|
|
|
|
|
def encode(hrp, witver, witprog): |
|
"""Encode a segwit address.""" |
|
ret = bech32_encode(hrp, [witver] + convertbits(witprog, 8, 5)) |
|
if decode(hrp, ret) == (None, None): |
|
return None |
|
return ret
|
|
|