(Solved): (2 marks) Exercise E: Hill cipher (cryptography). The Hill cipher is a cipher based on linear algeb ...

(2 marks) Exercise E: Hill cipher (cryptography). The Hill cipher is a cipher based on linear algebra. Invented by Lester S. Hill in 1929. Watch this Youtube video that discusses matrix encryption (a version of the Hill cipher) and answer the following questions: 1. Why do we need the key matrix to be invertible? 2. Why do we need the message to be a matrix with two rows? 3. Is $A=\left[\begin{array}{ll}3& 6\\ 2& 4\end{array}\right]$ a good key? Why? Why not? Justify your answer.