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# Copyright (c) 2017 Pieter Wuille
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""Reference implementation for Bech32 and segwit addresses."""
from typing import Iterable, List, Optional, Tuple, Union
import hashlib
CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
def bech32_polymod(values: Iterable[int]) -> int:
"""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: str) -> List[int]:
"""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: str, data: Iterable[int]) -> bool:
"""Verify a checksum given HRP and converted data characters."""
return bech32_polymod(bech32_hrp_expand(hrp) + list(data)) == 1
def bech32_create_checksum(hrp: str, data: Iterable[int]) -> List[int]:
"""Compute the checksum values given HRP and data."""
values = bech32_hrp_expand(hrp) + list(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: str, data: Iterable[int]) -> str:
"""Compute a Bech32 string given HRP and data values."""
combined = list(data) + bech32_create_checksum(hrp, data)
return hrp + "1" + "".join([CHARSET[d] for d in combined])
def bech32_decode(bech: str) -> Union[Tuple[None, None], Tuple[str, List[int]]]:
"""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 > 83 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: Iterable[int], frombits: int, tobits: int, pad: bool = True) -> Optional[List[int]]:
"""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: str, addr: str) -> Union[Tuple[None, None], Tuple[int, List[int]]]:
"""Decode a segwit address."""
hrpgot, data = bech32_decode(addr)
if hrpgot != hrp:
return (None, None)
assert data is not 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: str, witver: int, witprog: Iterable[int]) -> Optional[str]:
"""Encode a segwit address."""
five_bit_witprog = convertbits(witprog, 8, 5)
if five_bit_witprog is None:
return None
ret = bech32_encode(hrp, [witver] + five_bit_witprog)
if decode(hrp, ret) == (None, None):
return None
return ret
pubkey = "3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d"
squashed = convertbits(bytes.fromhex(pubkey), 8, 5)
print(bech32_encode("npub", squashed) == "npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6")
print(bech32_verify_checksum("npub", squashed))
hrp, data = bech32_decode("npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6")
data8bits = convertbits(data, 5, 8)[:-1]
reconstructed = bytes(data8bits).hex()
print(reconstructed)
print(pubkey)
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