4. Mutual Authentication using Symmetric Key (16 Points] (a) Consider the following mutual authentication protocol, where KAB is a shared symmetric key. "I'm Alice", R E(R, KAB) E(R+1,KAB) Alice Bob Give two different attacks that Trudy can use to convince Bob that she is Alice. (b) Consider the following protocol, where KAB is a shared symmetric key, CLNT and SRVR are constants, and K = h(S.RARE) is the session key. "I'm Alice", RA RE E(S, KAB), E(CLNT,K) E(SRVR,K) Alice Bob (i) Does Alice authenticate Bob? Justify your answer. (ii) Does Bob authenticate Alice? Justify your