Encryption Matrices are commonly used to encrypt data. Here is a simple form such an encryption can take. First, we represent ea
ch letter in the alphabet by a number, so let us take < space > = 0, A = 1, B = 2, and so on. Thus, for example, "ABORT MISSION" becomes [1 2 15 18 20 0 13 9 19 19 9 15 14]. To encrypt this coded phrase, we use an invertible matrix of any size with integer entries. For instance, let us take A to be the 2 × 2 matrix 3 4 1 2 . We can first arrange the coded sequence of numbers in the form of a matrix with two rows (using zero in the last place if we have an odd number of characters) and then multiply on the left by A. Encrypted Matrix = 3 4 1 2 1 15 20 13 19 9 14 2 18 0 9 19 15 0 = 11 117 60 75 133 87 42 5 51 20 31 57 39 14 , which we can also write as [11 5 117 51 60 20 75 31 133 57 87 39 42 14]. To decipher the encoded message, multiply the encrypted matrix by A−1. The following exercise uses the above matrix A for encoding and decoding. Use the matrix A to encode the phrase "GO TO PLAN B".
