In another situation, if an MITM attack occurs between the master node and a slave node during the second handshaking step in Phase IV, the attacker has already captured all the messages. However, since the attacker does not own the private key MN_Prv of the master node, he cannot decrypt the message that contains the encryption information {SCA, SC_Key} for the further communication. The attacker may also attempt to carry out an MITM attack with a fake slave node in this handshaking step. Nevertheless, he will not be authenticated by the master node, because he does not have the private key of the slave node to encrypt the random message CA_Rand, which acts as the fingerprint of the slave nodes.