Decode minikeys (like Casascius coin ones)

bitcoin/base58.py

@@ -23,6 +23,7 @@
     _bord = lambda x: x
 
 import binascii
+from hashlib import sha256
 
 import bitcoin.core
 
@@ -91,6 +92,30 @@ def decode(s):
         else: break
     return b'\x00' * pad + res
 
+class InvalidMinikeyError(Base58Error):
+    """Raised for invalid minikeys"""
+    pass
+
+def decode_minikey(minikey):
+    """Decode minikey in str or bytes to standard base58 bytes
+
+    Minikeys are an old key format, for details see
+    https://en.bitcoin.it/wiki/Mini_private_key_format.
+    """
+    if isinstance(minikey, str):
+        minikey = minikey.encode('ascii')
+    length = len(minikey)
+    if length not in [22, 30]:
+        raise InvalidMinikeyError('Minikey length %d is not 22 or 30' % length)
+    h = sha256(minikey)
+    h_cs = h.copy()
+    h_cs.update(b'?')
+    checksum = _bord(h_cs.digest()[0])
+    if checksum != 0:
+        raise InvalidMinikeyError('Minikey checksum %s is not 0' % checksum)
+    versioned = b'\x80' + h.digest()
+    checked = versioned + sha256(sha256(versioned).digest()).digest()[:4]
+    return encode(checked)
 
 class Base58ChecksumError(Base58Error):
     """Raised on Base58 checksum errors"""
@@ -151,6 +176,8 @@ def __repr__(self):
         'InvalidBase58Error',
         'encode',
         'decode',
+        'InvalidMinikeyError',
+        'decode_minikey',
         'Base58ChecksumError',
         'CBase58Data',
 )

bitcoin/tests/test_base58.py

@@ -36,6 +36,37 @@ def test_encode_decode(self):
             self.assertEqual(act_base58, exp_base58)
             self.assertEqual(act_bin, exp_bin)
 
+class Test_minikey(unittest.TestCase):
+
+    valid_minikeys = [
+        ('S6c56bnXQiBjk9mqSYE7ykVQ7NzrRy', '5JPy8Zg7z4P7RSLsiqcqyeAF1935zjNUdMxcDeVrtU1oarrgnB7'),
+        ('SVY4eSFCF4tMtMohEkpXkoN9FHxDV7', '5JSyovgwfVcuFZBAp8LAta2tMsmscxXv3FvzvJWeKBfycLAmjuZ'),
+        ('S6c56bnXQiBjk9mqSYEa30', '5KM4V1haDBMEcgzPuAWdHSBAVAEJNp4he2meirV3JNvZz9aWBNH')
+    ]
+    invalid_minikeys = [
+        ('', 'Minikey length 0 is not 22 or 30'),
+        ('S6c56bnXQiBjk9mqSYE7ykVQ7NzrR', 'Minikey length 29 is not 22 or 30'),
+        ('S6c56bnXQiBjk9mqSYE7ykVQ7NzrRyz', 'Minikey length 31 is not 22 or 30'),
+        ('S6c56bnXQiBjk9mqSYE7ykVQ7NzrRz', 'Minikey checksum 213 is not 0'),
+        ('S6c56bnXQiBjk9mqSYE7yk', 'Minikey checksum 46 is not 0')
+    ]
+
+    def test_decode_minikey_bytes(self):
+        for minikey, exp_base58_key in self.valid_minikeys:
+            base58_key2 = decode_minikey(minikey.encode('ascii'))
+            self.assertEqual(base58_key2, exp_base58_key)
+
+    def test_decode_minikey_str(self):
+        for minikey, exp_base58_key in self.valid_minikeys:
+            base58_key = decode_minikey(minikey)
+            self.assertEqual(base58_key, exp_base58_key)
+
+    def test_invalid(self):
+        for minikey, msg in self.invalid_minikeys:
+            with self.assertRaises(InvalidMinikeyError) as cm:
+                decode_minikey(minikey)
+            self.assertEqual(str(cm.exception), msg)
+
 class Test_CBase58Data(unittest.TestCase):
     def test_from_data(self):
         b = CBase58Data.from_bytes(b"b\xe9\x07\xb1\\\xbf'\xd5BS\x99\xeb\xf6\xf0\xfbP\xeb\xb8\x8f\x18", 0)

examples/minikey.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2013-2015 The python-bitcoinlib developers
+#
+# This file is part of python-bitcoinlib.
+#
+# It is subject to the license terms in the LICENSE file found in the top-level
+# directory of this distribution.
+#
+# No part of python-bitcoinlib, including this file, may be copied, modified,
+# propagated, or distributed except according to the terms contained in the
+# LICENSE file.
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from bitcoin import base58
+
+def parser():
+    import argparse
+    parser = argparse.ArgumentParser(
+        description='Decode a minikey to base58 format.',
+        epilog='Security warning: arguments may be visible to other users on the same host.')
+    parser.add_argument(
+        'minikey',
+        help='the minikey')
+    return parser
+
+if __name__ == '__main__':
+    args = parser().parse_args()
+    try:
+        base58_key = base58.decode_minikey(args.minikey)
+    except Exception as error:
+        print('%s: %s' % (error.__class__.__name__, str(error)))
+        exit(1)
+    else:
+        print(base58_key)