Give brief explanations for the following: (a) In PGP, suppose a user has two di erent public keys generated at random. Calculate the probability that these two keys will have the same key ID? (b) Explain briefly how PGP stores a user's private key. (c) Explain how SSL counters the threat of a replay attack i.e. what is to prevent replay of earlier SSL handshake messages. (d) Suppose SSL is used in your browser when you log in to your bank's website. Suppose the SSL handshake protocol has been completed and now, before the bank lets you log in, it asks you for a password. Now further suppose that the bad guy is eavesdropping - will he be able to gure out what the password is and log in as you next time? Give a YES/NO answer and then briefly explain your answer. (e) We have seen that in di erent protocols, either time stamps or nonces may be used to prevent replay attacks. What are the relative advantages of each i.e. explain one advantage time stamps have over nonces and one advantage nonces have over time stamps