Authentication steps of Wired Equivalent Privacy (WEP) as shown in the following Figure. The client (STA) sends a message to the accsess point (AP)requesting authentication. The AP issues a challenge,...

Authentication steps of Wired Equivalent Privacy (WEP) as shown in the following Figure. The client (STA) sends a message to the accsess point (AP)requesting authentication. The AP issues a challenge, which is a sequence of128 random bytes sent as plaintext. The STA encrypts the challenge with theshared key and returns it to the AP. The AP decrypts the incoming value and compares it to the challenge that it sent. If there is a match, the AP confirms that authentication has succeeded.a. What are the benefits of this authentication scheme?b. This authentication scheme is incomplete. What is missing and why is thisimportant? Hint: The addition of one or two messages would fix the problem.c. What is a cryptographic weakness of this scheme?2. In the four-way handshake protocol, suppose that the client and AP havefinished the protocol half-way through. That is, the client has receivedmessage1 from the AP and the AP has received message2 from the client. Nowthe attacker impersonates the AP and sends (AMAC, ANonce’, sn) to the clientbefore the client receives message3 from the AP. Explain what will happen?Suggest an efficient way to fix the problem.3. In Bluetooth secure pairing, the attacker may initiate the authenticationprocedure with a legitimate device over and over again and eventually guess thecorrect PIN. To prevent this from happening, each Bluetooth device oftenmaintains a blacklist of bad device addresses that failed to authenticatethemselves. The attacker can take advantage of this mechanism to launch adenial-of-service attack. Describe this attack.4. Why is TESLA not appropriate for wireless sensor networks? Discuss thetechniques that can be used to adapt TESLA for wireless sensor networks.5. It is possible to use a hash function to construct a block cipher with a structuresimilar to Feistel structure for instance DES. Because a hash function is oneway and a block cipher must be reversible (to decrypt), how is it possible?