tadd segwit bech32 module - electrum - Electrum Bitcoin wallet
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---
DIR commit e853dde1113f5d3fb96b864aca283781abbd6f8e
DIR parent 794baa16c8a13319b1e1a232998505054de3f626
HTML Author: ThomasV <thomasv@electrum.org>
Date: Wed, 30 Aug 2017 06:22:19 +0200
add segwit bech32 module
Diffstat:
A lib/segwit_addr.py | 122 +++++++++++++++++++++++++++++++
1 file changed, 122 insertions(+), 0 deletions(-)
---
DIR diff --git a/lib/segwit_addr.py b/lib/segwit_addr.py
t@@ -0,0 +1,122 @@
+# 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."""
+
+
+CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+
+
+def bech32_polymod(values):
+ """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):
+ """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, data):
+ """Verify a checksum given HRP and converted data characters."""
+ return bech32_polymod(bech32_hrp_expand(hrp) + data) == 1
+
+
+def bech32_create_checksum(hrp, data):
+ """Compute the checksum values given HRP and data."""
+ values = bech32_hrp_expand(hrp) + 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, data):
+ """Compute a Bech32 string given HRP and data values."""
+ combined = data + bech32_create_checksum(hrp, data)
+ return hrp + '1' + ''.join([CHARSET[d] for d in combined])
+
+
+def bech32_decode(bech):
+ """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 + 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, 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 = bech32_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 = bech32_encode(hrp, [witver] + convertbits(witprog, 8, 5))
+ assert decode(hrp, ret) is not (None, None)
+ return ret