electrum

Electrum Bitcoin wallet
git clone https://git.parazyd.org/electrum
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segwit_addr.py (4616B)

      1 
      2 # Copyright (c) 2017 Pieter Wuille
      3 #
      4 # Permission is hereby granted, free of charge, to any person obtaining a copy
      5 # of this software and associated documentation files (the "Software"), to deal
      6 # in the Software without restriction, including without limitation the rights
      7 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
      8 # copies of the Software, and to permit persons to whom the Software is
      9 # furnished to do so, subject to the following conditions:
     10 #
     11 # The above copyright notice and this permission notice shall be included in
     12 # all copies or substantial portions of the Software.
     13 #
     14 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     15 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     16 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     17 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     18 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     19 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     20 # THE SOFTWARE.
     21 
     22 """Reference implementation for Bech32 and segwit addresses."""
     23 
     24 
     25 CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
     26 _CHARSET_INVERSE = {x: CHARSET.find(x) for x in CHARSET}
     27 
     28 
     29 def bech32_polymod(values):
     30     """Internal function that computes the Bech32 checksum."""
     31     generator = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3]
     32     chk = 1
     33     for value in values:
     34         top = chk >> 25
     35         chk = (chk & 0x1ffffff) << 5 ^ value
     36         for i in range(5):
     37             chk ^= generator[i] if ((top >> i) & 1) else 0
     38     return chk
     39 
     40 
     41 def bech32_hrp_expand(hrp):
     42     """Expand the HRP into values for checksum computation."""
     43     return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp]
     44 
     45 
     46 def bech32_verify_checksum(hrp, data):
     47     """Verify a checksum given HRP and converted data characters."""
     48     return bech32_polymod(bech32_hrp_expand(hrp) + data) == 1
     49 
     50 
     51 def bech32_create_checksum(hrp, data):
     52     """Compute the checksum values given HRP and data."""
     53     values = bech32_hrp_expand(hrp) + data
     54     polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ 1
     55     return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)]
     56 
     57 
     58 def bech32_encode(hrp, data):
     59     """Compute a Bech32 string given HRP and data values."""
     60     combined = data + bech32_create_checksum(hrp, data)
     61     return hrp + '1' + ''.join([CHARSET[d] for d in combined])
     62 
     63 
     64 def bech32_decode(bech: str, ignore_long_length=False):
     65     """Validate a Bech32 string, and determine HRP and data."""
     66     bech_lower = bech.lower()
     67     if bech_lower != bech and bech.upper() != bech:
     68         return (None, None)
     69     pos = bech.rfind('1')
     70     if pos < 1 or pos + 7 > len(bech) or (not ignore_long_length and len(bech) > 90):
     71         return (None, None)
     72     # check that HRP only consists of sane ASCII chars
     73     if any(ord(x) < 33 or ord(x) > 126 for x in bech[:pos+1]):
     74         return (None, None)
     75     bech = bech_lower
     76     hrp = bech[:pos]
     77     try:
     78         data = [_CHARSET_INVERSE[x] for x in bech[pos+1:]]
     79     except KeyError:
     80         return (None, None)
     81     if not bech32_verify_checksum(hrp, data):
     82         return (None, None)
     83     return (hrp, data[:-6])
     84 
     85 
     86 def convertbits(data, frombits, tobits, pad=True):
     87     """General power-of-2 base conversion."""
     88     acc = 0
     89     bits = 0
     90     ret = []
     91     maxv = (1 << tobits) - 1
     92     max_acc = (1 << (frombits + tobits - 1)) - 1
     93     for value in data:
     94         if value < 0 or (value >> frombits):
     95             return None
     96         acc = ((acc << frombits) | value) & max_acc
     97         bits += frombits
     98         while bits >= tobits:
     99             bits -= tobits
    100             ret.append((acc >> bits) & maxv)
    101     if pad:
    102         if bits:
    103             ret.append((acc << (tobits - bits)) & maxv)
    104     elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
    105         return None
    106     return ret
    107 
    108 
    109 def decode(hrp, addr):
    110     """Decode a segwit address."""
    111     if addr is None:
    112         return (None, None)
    113     hrpgot, data = bech32_decode(addr)
    114     if hrpgot != hrp:
    115         return (None, None)
    116     decoded = convertbits(data[1:], 5, 8, False)
    117     if decoded is None or len(decoded) < 2 or len(decoded) > 40:
    118         return (None, None)
    119     if data[0] > 16:
    120         return (None, None)
    121     if data[0] == 0 and len(decoded) != 20 and len(decoded) != 32:
    122         return (None, None)
    123     return (data[0], decoded)
    124 
    125 
    126 def encode(hrp, witver, witprog):
    127     """Encode a segwit address."""
    128     ret = bech32_encode(hrp, [witver] + convertbits(witprog, 8, 5))
    129     assert decode(hrp, ret) != (None, None)
    130     return ret