Task Three: Analysis of Substitution Cipher (2 marks) Consider the following mapping A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Can the function f (x) = xk (mod 26) be used as a cipher where k > 1 is the key and x is a letter to be encrypted? Justify your