Suppоse Alice wаnts tо send аn e-mаil tо Bob. Bob has a public-private key pair (KB+, KB- ), 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. A. [2 points] In this situation, is it possible to design a scheme so that Bob can verify that Alice created the message? If so, briefly explain your design. B. [3 points] Is it possible to design a scheme that provides confidentiality for sending the message from Alice to Bob? If so, briefly explain your design.