Question 3 (Brief answer): Suppose Bob has the following protocol for authenticating Alice I'm Alice Challenge R Encrypt(R)K Alice Bob 0 The first two messages are sent in plaintext. The third message Encrypt(R): contains a message with R encrypted by a secret key K that only Bob and Alice know. It uses a private key encryption protocol a) Is this protocol secure? Why or why not? How can you make the protocol more secure without using public key encryption? b)