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'''Base58 encoding
Implementations of Base58 and Base58Check encodings that are compatible
with the bitcoin network.
'''
# This module is based upon base58 snippets found scattered over many bitcoin
# tools written in python. From what I gather the original source is from a
# forum post by Gavin Andresen, so direct your praise to him.
# This module adds shiny packaging and support for python3.
from functools import lru_cache
from hashlib import sha256
from typing import Mapping, Union
__version__ = '2.1.1'
# 58 character alphabet used
BITCOIN_ALPHABET = \
b'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
RIPPLE_ALPHABET = b'rpshnaf39wBUDNEGHJKLM4PQRST7VWXYZ2bcdeCg65jkm8oFqi1tuvAxyz'
XRP_ALPHABET = RIPPLE_ALPHABET
# Retro compatibility
alphabet = BITCOIN_ALPHABET
def scrub_input(v: Union[str, bytes]) -> bytes:
if isinstance(v, str):
v = v.encode('ascii')
return v
def b58encode_int(
i: int, default_one: bool = True, alphabet: bytes = BITCOIN_ALPHABET
) -> bytes:
"""
Encode an integer using Base58
"""
if not i and default_one:
return alphabet[0:1]
string = b""
base = len(alphabet)
while i:
i, idx = divmod(i, base)
string = alphabet[idx:idx+1] + string
return string
def b58encode(
v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET
) -> bytes:
"""
Encode a string using Base58
"""
v = scrub_input(v)
origlen = len(v)
v = v.lstrip(b'\0')
newlen = len(v)
acc = int.from_bytes(v, byteorder='big') # first byte is most significant
result = b58encode_int(acc, default_one=False, alphabet=alphabet)
return alphabet[0:1] * (origlen - newlen) + result
@lru_cache()
def _get_base58_decode_map(alphabet: bytes,
autofix: bool) -> Mapping[int, int]:
invmap = {char: index for index, char in enumerate(alphabet)}
if autofix:
groups = [b'0Oo', b'Il1']
for group in groups:
pivots = [c for c in group if c in invmap]
if len(pivots) == 1:
for alternative in group:
invmap[alternative] = invmap[pivots[0]]
return invmap
def b58decode_int(
v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET, *,
autofix: bool = False
) -> int:
"""
Decode a Base58 encoded string as an integer
"""
if b' ' not in alphabet:
v = v.rstrip()
v = scrub_input(v)
map = _get_base58_decode_map(alphabet, autofix=autofix)
decimal = 0
base = len(alphabet)
try:
for char in v:
decimal = decimal * base + map[char]
except KeyError as e:
raise ValueError(
"Invalid character {!r}".format(chr(e.args[0]))
) from None
return decimal
def b58decode(
v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET, *,
autofix: bool = False
) -> bytes:
"""
Decode a Base58 encoded string
"""
v = v.rstrip()
v = scrub_input(v)
origlen = len(v)
v = v.lstrip(alphabet[0:1])
newlen = len(v)
acc = b58decode_int(v, alphabet=alphabet, autofix=autofix)
result = []
while acc > 0:
acc, mod = divmod(acc, 256)
result.append(mod)
return b'\0' * (origlen - newlen) + bytes(reversed(result))
def b58encode_check(
v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET
) -> bytes:
"""
Encode a string using Base58 with a 4 character checksum
"""
v = scrub_input(v)
digest = sha256(sha256(v).digest()).digest()
return b58encode(v + digest[:4], alphabet=alphabet)
def b58decode_check(
v: Union[str, bytes], alphabet: bytes = BITCOIN_ALPHABET, *,
autofix: bool = False
) -> bytes:
'''Decode and verify the checksum of a Base58 encoded string'''
result = b58decode(v, alphabet=alphabet, autofix=autofix)
result, check = result[:-4], result[-4:]
digest = sha256(sha256(result).digest()).digest()
if check != digest[:4]:
raise ValueError("Invalid checksum")
return result
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