QUESTION 2 [23 Marks (a) Ahmad and Ben want to have a secured communication between them. Before sending any email, the messages will be encrypted with double encryption. Both of encryption. Given the encrypted message received by Ben is, Ct"BNY them have agreed to apply Playfair cipher for the first encryption and Vigenere cipher as the second YB XZHMZ HOFIE FVREI LKJQx c", knowing that it was obtained by applying first the Playfair cipher using the key, K LOST TIME IS NEVER FOUND AGAIN, and then using the Vigenere cipher with the key, K" JYXYVI". ) Ahmad has encrypted K to make sure the integrity of the delivered messages. Given the encrypted K2 is JYXYVI, Ben is required to decrypt K2 using Caesar Cipher. Write the plaintext which will be generated from the encryption key [3 Marks] (ii) Write the plaintext messages from the above cryptogram, C after successfully [9 Marks] i hat you are obtaining the K2 in (i). Reference provided in Appendix A. (b) You want to establish a secure communication w th Alice. In order to do t going to use Diffie-Hellman key arrangement protocol with the following step. 1. You and Alice agree on using prime number, n 467 and root number, g 2. Alice sends you the public key which is keypabb 30 3. You choose keypi ag 9 asyour private key mpute your public key and the common key for Diffei-Hellman arrangemen [8 Marks] Assume that it was not Alice but Oscar who sent you his public key, keypb bo G) Co protocol. 30 in Step 2. Name the attack and give justification whether it is successful or (3 Marks] not