3. Bob is arguing that if you use output feedback (OFB) mode twice in a row to encrypt a long message, M, using the same key each time, it will be more secure. Explain why Bob is wrong, no matter what encryption algorithm he is using for block encryption (15 points). 4. Suppose you wish to encrypt the message, M 42 using RSA encryption. Given a public key where p 23 and q 11 and the relative prime e - 7. Find n, and show all necessary steps to encrypt your message (42). (Hint: check p.411 of the text for information on public key RSA) (15 points) 5. Now suppose you receive an encrypted message, C 287. Given that p 13 and q 29 and that e -5, show all necessary steps to decrypt the message, and then give the final plaintext decryption of the message. (15 points)