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