diff options
Diffstat (limited to 'scripts/bech.py')
| -rw-r--r-- | scripts/bech.py | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/scripts/bech.py b/scripts/bech.py new file mode 100644 index 0000000..b2e3dcb --- /dev/null +++ b/scripts/bech.py @@ -0,0 +1,144 @@ +# 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)
\ No newline at end of file |