Add blech32 python implementation with diff annotation with segwit_addr.py

test/functional/test_framework/liquid_addr.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+# Copyright (c) 2017 Pieter Wuille
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Reference implementation for Blech32 and segwit addresses."""
+
+
+CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+
+def blech32_polymod(values):
+    """Internal function that computes the blech32 checksum."""
+    generator = [0x7d52fba40bd886, 0x5e8dbf1a03950c, 0x1c3a3c74072a18, 0x385d72fa0e5139, 0x7093e5a608865b] # new generators, 7 bytes
+    chk = 1
+    for value in values:
+        top = chk >> 55 # 25->55
+        chk = ((chk & 0x7fffffffffffff) << 5) ^^ value # 0x1ffffff->0x7fffffffffffff
+        for i in range(5):
+            chk ^= generator[i] if ((top >> i) & 1) else 0
+    return chk
+
+
+def blech32_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 blech32_verify_checksum(hrp, data):
+    """Verify a checksum given HRP and converted data characters."""
+    return blech32_polymod(blech32_hrp_expand(hrp) + data) == 1
+
+
+def blech32_create_checksum(hrp, data):
+    """Compute the checksum values given HRP and data."""
+    values = blech32_hrp_expand(hrp) + data
+    polymod = blech32_polymod(values + [0]*12) ^^ 1 # 6->12
+    return [(polymod >> 5 * (11 - i)) & 31 for i in range(12)]
+#                            ^ 5                          ^ 6
+
+def blech32_encode(hrp, data):
+    """Compute a blech32 string given HRP and data values."""
+    combined = data + blech32_create_checksum(hrp, data)
+    return hrp + '1' + ''.join([CHARSET[d] for d in combined])
+
+
+def blech32_decode(bech):
+    """Validate a blech32 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 + 13 > len(bech) or len(bech) > 1000: # 7->13 90->1000
+        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 blech32_verify_checksum(hrp, data):
+        return (None, None)
+    return (hrp, data[:-12]) # 6->12
+
+
+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 = blech32_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 = blech32_encode(hrp, [witver] + convertbits(witprog, 8, 5))
+    if decode(hrp, ret) == (None, None):
+        return None
+    return ret