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Add blech32 python implementation with diff annotation with segwit_ad…

…dr.py
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instagibbs authored and stevenroose committed Mar 1, 2019
1 parent 17a22f1 commit 9cb2fa051fcbe0fe66f15e6b88d224d1935376f4
Showing with 106 additions and 0 deletions.
  1. +106 −0 test/functional/test_framework/liquid_addr.py
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#!/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 Blech32 and segwit addresses."""


CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"

def blech32_polymod(values):
"""Internal function that computes the blech32 checksum."""
generator = [0x7d52fba40bd886, 0x5e8dbf1a03950c, 0x1c3a3c74072a18, 0x385d72fa0e5139, 0x7093e5a608865b] # new generators, 7 bytes
chk = 1
for value in values:
top = chk >> 55 # 25->55
chk = ((chk & 0x7fffffffffffff) << 5) ^^ value # 0x1ffffff->0x7fffffffffffff
for i in range(5):
chk ^= generator[i] if ((top >> i) & 1) else 0
return chk


def blech32_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 blech32_verify_checksum(hrp, data):
"""Verify a checksum given HRP and converted data characters."""
return blech32_polymod(blech32_hrp_expand(hrp) + data) == 1


def blech32_create_checksum(hrp, data):
"""Compute the checksum values given HRP and data."""
values = blech32_hrp_expand(hrp) + data
polymod = blech32_polymod(values + [0]*12) ^^ 1 # 6->12
return [(polymod >> 5 * (11 - i)) & 31 for i in range(12)]
# ^ 5 ^ 6

def blech32_encode(hrp, data):
"""Compute a blech32 string given HRP and data values."""
combined = data + blech32_create_checksum(hrp, data)
return hrp + '1' + ''.join([CHARSET[d] for d in combined])


def blech32_decode(bech):
"""Validate a blech32 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 + 13 > len(bech) or len(bech) > 1000: # 7->13 90->1000
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 blech32_verify_checksum(hrp, data):
return (None, None)
return (hrp, data[:-12]) # 6->12


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 = blech32_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 = blech32_encode(hrp, [witver] + convertbits(witprog, 8, 5))
if decode(hrp, ret) == (None, None):
return None
return ret

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