The following figure illustrates a protocol between two agents A ans B and a server S$.$ The intent is to get the server to generate a shared session key Kab, and also to enaB. The following figure illustrates a protocol between two agents A and $B,$ und a server $S.$ The

intent is to get the server to generate a shared session key $K_{Ar},$ and to also enable A and $B$ to

make sure they are communicating with each other. Each agent shares a private key with the

server $S$:A has $K_{is},$ and $B$ has $K_{is}.R_{if}$ and $R_b$ values are randomly generated "nonces"