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# Copyright (c) 2016-2017, Neil Booth
#
# All rights reserved.
#
# The MIT License (MIT)
#
# 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.
'''Cryptograph hash functions and related classes.'''
import hashlib
import hmac
from lib.util import bytes_to_int, int_to_bytes
def sha256(x):
'''Simple wrapper of hashlib sha256.'''
assert isinstance(x, (bytes, bytearray, memoryview))
return hashlib.sha256(x).digest()
def ripemd160(x):
'''Simple wrapper of hashlib ripemd160.'''
assert isinstance(x, (bytes, bytearray, memoryview))
h = hashlib.new('ripemd160')
h.update(x)
return h.digest()
def double_sha256(x):
'''SHA-256 of SHA-256, as used extensively in bitcoin.'''
return sha256(sha256(x))
def hmac_sha512(key, msg):
'''Use SHA-512 to provide an HMAC.'''
return hmac.new(key, msg, hashlib.sha512).digest()
def hash160(x):
'''RIPEMD-160 of SHA-256.
Used to make bitcoin addresses from pubkeys.'''
return ripemd160(sha256(x))
def hash_to_str(x):
'''Convert a big-endian binary hash to displayed hex string.
Display form of a binary hash is reversed and converted to hex.
'''
return bytes(reversed(x)).hex()
def hex_str_to_hash(x):
'''Convert a displayed hex string to a binary hash.'''
return bytes(reversed(bytes.fromhex(x)))
class Base58Error(Exception):
'''Exception used for Base58 errors.'''
class Base58(object):
'''Class providing base 58 functionality.'''
chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
assert len(chars) == 58
cmap = {c: n for n, c in enumerate(chars)}
@staticmethod
def char_value(c):
val = Base58.cmap.get(c)
if val is None:
raise Base58Error('invalid base 58 character "{}"'.format(c))
return val
@staticmethod
def decode(txt):
"""Decodes txt into a big-endian bytearray."""
if not isinstance(txt, str):
raise Base58Error('a string is required')
if not txt:
raise Base58Error('string cannot be empty')
value = 0
for c in txt:
value = value * 58 + Base58.char_value(c)
result = int_to_bytes(value)
# Prepend leading zero bytes if necessary
count = 0
for c in txt:
if c != '1':
break
count += 1
if count:
result = bytes(count) + result
return result
@staticmethod
def encode(be_bytes):
"""Converts a big-endian bytearray into a base58 string."""
value = bytes_to_int(be_bytes)
txt = ''
while value:
value, mod = divmod(value, 58)
txt += Base58.chars[mod]
for byte in be_bytes:
if byte != 0:
break
txt += '1'
return txt[::-1]
@staticmethod
def decode_check(txt):
'''Decodes a Base58Check-encoded string to a payload. The version
prefixes it.'''
be_bytes = Base58.decode(txt)
result, check = be_bytes[:-4], be_bytes[-4:]
if check != double_sha256(result)[:4]:
raise Base58Error('invalid base 58 checksum for {}'.format(txt))
return result
@staticmethod
def encode_check(payload):
"""Encodes a payload bytearray (which includes the version byte(s))
into a Base58Check string."""
assert isinstance(payload, (bytes, bytearray, memoryview))
be_bytes = payload + double_sha256(payload)[:4]
return Base58.encode(be_bytes)