Affine Cryptosystem with $2-$letter basic units.

All arithmetic is done in $Z_{26}.x$ is a $21$ matrix below.

Encryption function: $f_E(x)=x+mod26$

Here $=\left[\begin{array}{cc}22& 5\\ 21& 10\end{array}\right]$ and $=\left[\begin{array}{c}18\\ 11\end{array}\right]($ and $$ are kept secret in practice$)$

Encrypt 'AIRE' with this system.

worked solution $-$ we encrypt Al first: Aharr$0$ agus Iharr$8$; therefore $x=\left[\begin{array}{c}0\\ 8\end{array}\right]$ here $f_E\left[\begin{array}{c}6\\ 13\end{array}\right]$harrGN

AIRE $f_E$

$($input a $4$ letter string: $2+2)$

Encrypt 'PANDAS' with this affine system. PANDAS $f_E$

$($input a six letter string: $2+2+2)$