11. In a RSA system, p=5, q=11. Find out all the possible values of e. (1%) 12. Alice and Bob want to securely communicate with a session key K, distributed by a key distribution centre. Bob decides to initiate the process by requesting the session key for both of them. Write a protocol with proper assumption for the session key distribution that meets the following requirements: (1%) (a) Confidentiality (b) Freshness (c) Authentication 13. Alice sends Bob the following message: Ek [ME KUbH (M)]] Explain what preparation needs to be done before this message can be sent? (1%) 14. Design a message authentication protocol by hash and encryption to ensure confi- dentiality and authentication. (1%) 15. In Kerberos, the client sends the server the following message which contains two parts: Tickety, Authenticatorc What is the function of each part? Does the server need to perform the decryption in order? Why? (1%)