Cryptography Help Please.

please answer last 2 questions in the very end after D) sub question thank you.

4. (15 points) Alice and Bob shared an n-bit secret key some time ago. Now they are no longer sure they stil have the same key. Thus, they use the following method to communicate with each other over an insecure channel to verify that the key KAB held by Alice is the same as the key KBA held by Bob. Their goal is to prevent an attacker from learning the secret key. (a) Alice generates a random n-bit value AR. (b) Alice computes X KAL R, where o is the bit-wise exclusive or operator, and sends X to Bob. (c) Bob computes Y-KBA and sends Y to Alice. (d) Alice compares R and Y. If R = Y, she concludes that KAB = KBA, that is, she and Bob have indeed the same secret key. Consider the following two sub-questions: (5 points) Suppose indeed KAB KBA. Show that this protocol is not secure. (10 points) Suppose indeed KAB KBA. Describe a situation in which the above infor- mation can be exploited to launch further attacks 4. (15 points) Alice and Bob shared an n-bit secret key some time ago. Now they are no longer sure they stil have the same key. Thus, they use the following method to communicate with each other over an insecure channel to verify that the key KAB held by Alice is the same as the key KBA held by Bob. Their goal is to prevent an attacker from learning the secret key. (a) Alice generates a random n-bit value AR. (b) Alice computes X KAL R, where o is the bit-wise exclusive or operator, and sends X to Bob. (c) Bob computes Y-KBA and sends Y to Alice. (d) Alice compares R and Y. If R = Y, she concludes that KAB = KBA, that is, she and Bob have indeed the same secret key. Consider the following two sub-questions: (5 points) Suppose indeed KAB KBA. Show that this protocol is not secure. (10 points) Suppose indeed KAB KBA. Describe a situation in which the above infor- mation can be exploited to launch further attacks