Activity $2($Design your awn substitution cipher$)$

$($a$)$ Use the criteria indicated to create a pair of $33$ matrices $(D$&$D^{-1}),$ where the entries of the matrix $D$ are all integers.

$(20$ marks$)$

$($i$),d_{21}=5$

$($ii$)d_{12}=-2$

$($b$)$ Create your own substitution cipher. Then use it and the matrix $D$ you created in $($a$)$ to encrypt the titie of your favourite movie.

$(20$ marks$)$

$($c$)$ Use the matrix $D^{\text{'}}$ and the appropriate substitution cipher to decrynt the message from $($b$).(20$ marks$)$