1. Suppose Alice wants to send an e-mail to Bob. Bob has a public-private key pair ( K B + , K B -), and Alice has Bob’s certificate. But Alice does not have a public, private key pair. Alice and Bob...

1. Suppose Alice wants to send an e-mail to Bob. Bob has a public-private key pair (K
_B
⁺,
K_B

-), and Alice has Bob’s certificate. But Alice does not have a public, private key pair. Alice and Bob (and the entire world) share the same hash function H( ).

a. In this situation, is it possible to design a scheme so that Bob can verify that Alice created the message? If so, show how with a block diagram for Alice and Bob.

b. Is it possible to design a scheme that provides confidentiality for sending the message from Alice to Bob? If so, show how with a block diagram for Alice and Bob.