def METHOD_NAME(self):
    """Last authentication step."""
    session_key = binascii.unhexlify(self.session.key)
    aes_key = hash_sha512("Pair-Setup-AES-Key", session_key)[0:16]
    tmp = bytearray(hash_sha512("Pair-Setup-AES-IV", session_key)[0:16])
    _LOGGER.debug("Increase last byte from %d to %s", tmp[-1], tmp[-1] + 1)
    tmp[-1] = tmp[-1] + 1  # Last byte must be increased by 1
    aes_iv = bytes(tmp)
    log_binary(_LOGGER, "Pair-Setup-AES", Key=aes_key, IV=aes_iv)
    epk, tag = aes_encrypt(modes.GCM, aes_key, aes_iv, self._auth_public)
    log_binary(_LOGGER, "Pair-Setup EPK+Tag", EPK=epk, Tag=tag)
    return epk, tag