please solve a and b like required NOT calculation in details

(15 points) User Authentication. (a) (7 points) Consider the following proposed authentication protocol between Alice and Bob based on symmetric encryption with a trusted third party (TTP) which is supposed to establish a shared session key K between the two users. AliceTTP:Alice,BobTTPAlice:{K}KAT,{K}KBTAliceBob:{K}KBTBobAlice:{HelloAlice!ThisisBob}K Show an attack against this protocol by demonstrating a scenario where Eve can impersonate Bob to Alice (i.e. Alice will think they are talking to Bob when they are in fact talking to Eve). Then provide a fix to the protocol to prevent this attack. (b) (8 points) Consider the following proposed authentication protocol between Alice and Bob based on asymmetric encryption which is supposed to establish a shared session key K between the two users. Alice's public key is KA and Bob's public key is KB. AliceBob:{Alice,NA}KBBobAlice:{K,NA}KAAliceBob:{HelloBob!ThisisAlice,NA}K Show an attack against this protocol by demonstrating a scenario where Eve can impersonate Alice to Bob (i.e. Bob will think they are talking to Alice when they are in fact talking to Eve). Then provide a fix to the protocol to prevent this attack