Allorand Bob use a cipher for message encryption. Eve can find out the secret key by solving the following problem. The statest postie integer that 84 more than a rs, is the multiple of 7, and a multiple of 11 what is the secret key determined by Eve?

Introduction to Cryptography (CSE1007. 249M] Duration: 120 mil Marks: 60 Final Assessment Test Answer all the questions. [Note: Show stepwise solutions) Suppose that there exists a variant of Playfair cipher which supports both alphabets (a,b,2) and numbers (0,1,2...,9) for encryption and decryption. Design the key matrix and encrypt the message happy new year 2021" using the key "COVID20". Assume the same rules of encryption and decryption as that of normal Playfair cipher. Raju wants to send a message "W" to Shila confidentially. Raju and Shila decide to use Gamal public key cryptosystem. The parameters are selected as prime p = 109, e,= 6,0-7, and r-10. Explain the steps of key generation, encryption, and decryption, (Coding: 0, bul, =25] Aice and Bob use a symmetric key cipher for message encryption. Eve can find out the secret key by solving the following problem-"The smallest positive integer that is more than a multiple of 5,1 less than a multiple or 2 and a multiple of 11." What is the secret key determined by Eve? Krish wants to send a message"no" to Ananya. For authentication of the message origin, they use RSA-based digital signature scheme. Explain the steps of key generation, signing, and verification where p and are the 11 and 13 primes, respectively, e is selected as 343. (Coding: 0,1,.225] There are 80 constants (K, to generated in SHA-512 which are of 64 bits each. Find the constant Ka (Find at least 8 bits) ms 101 K vell