Part C: Matrices and Cryptograg. Matrices can

Cryptogr to code messages so that they can only be read after being deciphered by a key.

The first step is to decide on a key that can be used to encode the matrix. The key must be an $nn$ invertible matrix. The next step is to convert the message to numbers and write it as a matrix. Each letter of the alphabet is represented by a number $(A$ is $1,B$ is $2,$dots $).$ The number $0$ is used to represent a blank space. Finally, the message is encoded by multiplying it by the key.

Activity $1$

Use $\left[\begin{array}{cc}1& -2\\ -1& 3\end{array}\right]$ to encode the message "SATURDAY AT NOON

Step $1$: Convert the message to numbers and write it as a matrix. Remember to use the number $0$ for a space between each word. The first $3$ were done for you.

S$-19$ A$-1$ T$-20$

The key is a $22$ matrix. To make the matrix multiplication possible, write the message as an $82$ matrix.

$\backslash$table$[[S,A$