Suppose Alice wants to communicate with Bob using symmetric key cryptography using a session key Ks. In Section 8.2, we learned how public-key cryptography can be used to distribute the session key from Alice to Bob. In this problem, we explore how the session key can be distributed without public key cryptography using a Key Distribution Center (KDC). The KDC is a server that shares a unique secret symmetric key with each registered user. For Alice and Bob, denote these keys by KA-KDC and KB-KDC. Design a scheme that uses the KDC to distribute Ks to Alice and Bob. Your scheme should have use three messages to distribute the session key: a message Alice to KDC, a message from the KDC to Alice, and a message from Alice to Bob.