tsegwit_addr.py - electrum - Electrum Bitcoin wallet
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tsegwit_addr.py (4616B)
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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