def decode(b58: str) -> bytes:
partial_sum = 0
exponent = 0
for digit in reversed(b58):
try:
partial_sum += ALPHABET.index(digit) * BASE**exponent
except ValueError:
raise Base58DecodeError('Bad Byte') from None
exponent += 1
return int_to_bytes(partial_sum)
def var_int(n):
if n < 0xfd:
return int_to_bytes(n)
elif n <= 0xffff:
return b'\xfd' + pad(n, 2)[::-1]
elif n <= 0xffffffff:
return b'\xfe' + pad(n, 4)[::-1]
elif n <= 0xffffffffffffffff:
return b'\xff' + pad(n, 8)[::-1]
else:
raise ValueError('Data too long for var_int')
def child(self, i: int) -> 'Xprv':
hardened = i >= 1 << 31
if hardened:
I = hmac.new(key=self.code,
msg=self.keydata() +
int_to_bytes(i).rjust(32, b'\x00'),
digestmod=hashlib.sha512).digest()
else:
I = hmac.new(key=self.code,
msg=self.key.to_public().encode(compressed=True) +
int_to_bytes(i).rjust(32, b'\x00'),
digestmod=hashlib.sha512).digest()
I_L, I_R = bytes_to_int(I[:32]), I[32:]
key = I_L + self.key.int() % CURVE.N
if I_L >= CURVE.N or key == 0:
return self.child(i + 1)
ret_code = I_R
return Xprv(key, ret_code, depth=self.depth + 1, i=i)
def child(self, i: int) -> 'Xpub':
hardened = i >= 1 << 31
if hardened:
raise KeyDerivationError(
'Cannot derive a hardened key from a Public key')
I = hmac.new(key=self.code,
msg=self.keydata() + int_to_bytes(i).rjust(32, b'\x00'))
I_L, I_R = I[:32], I[32:]
key = PrivateKey(I_L).to_public().point + self.key.point
ret_code = I_R
# TODO add point at infinity check
return Xpub(key, ret_code, depth=self.depth + 1, i=i)
def witness_byte(witver: int) -> bytes:
assert 0 <= witver <= 16, "Witness version must be between 0-16"
return int_to_bytes(witver + 0x50 if witver > 0 else 0)
def byte(self):
return int_to_bytes(self.value)