The protocol referred to in Problem $16\mathrm{.}1$ can be reduced from seven steps to five, having the following sequence:

a$.$ A S B:

b$.$ A S KDC:

c$.$ KDC S B:

d$.$ B S A:

e$.$ A S B:Show the message transmitted at each step. Hint: The final message in this protocol is

the same as the final message in the original protocol.