CRYPTOGRAPHY

(b) Identify Z27={0,,25,26} with {A,,Z,} as in part (a). The ciphertext string NSRG was obtained using a 2-dimensional Hill cipher over Z27 with key [1115] Find the corresponding plaintext. [10 marks] (c) Describe what is meant by a brute force attack and describe a scenario where this is feasible. [5 marks] (d) An affine cipher (of dimension 1) over Z450 is used to encrypt messages. Find the number of possible keys. [5 marks]