def dec_next_char(self, passBytes) -> "Tuple[int, bytes]":
        """
        Decrypts the first byte of the password and returns the decrypted byte and the remaining bytes.
        Parameters
        ----------
        passBytes : bytes
            The password bytes
        """
        if not passBytes:
            return 0, passBytes
        a = passBytes[0]
        b = passBytes[1]
        passBytes = passBytes[2:]
        return ~(((a << 4) + b) ^ self.PW_MAGIC) & 0xFF, passBytes

        Decrypts the first byte of the password and returns the decrypted byte and the remaining bytes.
        Parameters
        ----------
        passBytes : bytes
            The password bytes
        
cme/modules/winscp_dump.py