Design a security protocol that will allow a Session key $(K_{ab})$ to be established between A and $B$ for use in a secure

chat service.

You can use Key Transport or Agreement in your design but you must specify$/$state which you are using in your

solution.

I want you to develop your own design on paper $($no programming necessary$)$ based on the conditions below.

Note: The session key should NOT be known to the Chat Server $($S$)$ and the Chat Server $($S$)$ should only forward the

encrypted messages to A and $B,$ as shown below.

The secure chat to be established between two entities A and B using a Chat Server $($S$)$ and session key $K_{ab}$ as below:

i$.$e$.$ A and B Never communicate directly but always go through the Chat Server $($S$).$

The following conditions apply to your protocol design.

A and $B$ do not communicate directly.

Each entity has a Public Key Certificate assigned to it$,$ i$.$e:$K_{ab})S{K}_{ab}$