Select one answer that is most appropriate. Partial credits may be given.

a$.$

Each party does the same thing: Generate a private key X using a pseudo$-$random number generator, compute Y$=$a$^$X mod p$,$ and transmit Y to the other party.

b$.$

When receiving Y from the other party, each party computes K $=$ Y$^$X mod p with his private X to obtain an identical key K$.$

c$.$

The Diffie$-$Hellman Key Exchange scheme is secure against man$-$in$-$the$-$middle attacks.

d$.$

Both a and b$.$

e$.$

Both b and c$.$

f$.$

All of the above.

g$.$

None of the above.