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@gitzhou

gitzhou/crypto.py

Last active Oct 19, 2020
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import hashlib
from binascii import hexlify
def sha256(payload: bytes) -> bytes:
return hashlib.sha256(payload).digest()
def double_sha256(payload: bytes) -> bytes:
return sha256(sha256(payload))
def double_sha256_checksum(payload: bytes) -> bytes:
return double_sha256(payload)[:4]
def ripemd160_sha256(payload: bytes) -> bytes:
return hashlib.new('ripemd160', sha256(payload)).digest()
BASE58_ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
def b58_encode(payload: bytes) -> str:
pad = 0
for byte in payload:
if byte == 0:
pad += 1
else:
break
prefix = '1' * pad
num = int.from_bytes(payload, 'big')
result = ''
while num > 0:
num, remaining = divmod(num, 58)
result = BASE58_ALPHABET[remaining] + result
return prefix + result
def b58check_encode(payload: bytes) -> str:
return b58_encode(payload + double_sha256_checksum(payload))
def int_to_bytes(num: int, byteorder: str = 'big') -> bytes:
"""Converts an int to the least number of bytes as possible."""
return num.to_bytes((num.bit_length() + 7) // 8 or 1, byteorder)
def b58_decode(encoded: str) -> bytes:
pad = 0
for char in encoded:
if char == '1':
pad += 1
else:
break
prefix = b'\x00' * pad
num = 0
try:
for char in encoded:
num *= 58
num += BASE58_ALPHABET.index(char)
except KeyError:
raise ValueError(f'Invalid base58 encoded "{encoded}"')
return prefix + int_to_bytes(num)
def b58check_decode(encoded: str) -> bytes:
decoded = b58_decode(encoded)
payload = decoded[:-4]
decoded_checksum = decoded[-4:]
hash_checksum = double_sha256_checksum(payload)
if decoded_checksum != hash_checksum:
raise ValueError(f'Decoded checksum {hexlify(decoded_checksum)} from "{hexlify(decoded)}" is not equal to hash checksum {hexlify(hash_checksum)}')
return payload
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