Q11) (ILO: C1) (7 Marks) Consider the following protocol: 1. A KDC: IDA II IDB II N1 2. KDC A: E(Ka[K II 1DB II Ny || E(K[K|| IDA])]) 3. AB: E(Kb, [Ks II IDA] 4. B - A: E(Ks, N2) 5. AB: E(Ks, f(N2)) Note: Ka and Kp are master keys; N1 and N2 are nonce; and Ks is session key. (a) Explain the protocol. (b) Can you think of a positive attack on this protocol? Explain how it can be done. (c) Mention a positive technique to get around the attack, not a detailed mechanism, just the basics of the idea