Alice wants to send a message m to Bob. Alice has a public key pair K+ A and K A . Bob wants to verify that the message he receives is indeed sent by Alice and the message is not altered to be any other message.

a. Can Alice send K A (m)?

b. Can Alice send m + K A (m) (+ denotes concatenation)?

c. If the above two methods do not work, how to achieve the goal? Assume that a hash function h() can be used.