Using the Vigenere cypher with the encryption table shown in Figure $3\mathrm{.}1$ and the key

computersecurity:

Figure $3\mathrm{.}1$

$($a$)$ Encrypt the message "Today is a good day." with an explanation of your method. $[10\%]$

$($b$)$ Decrypt the message "Icas fngb omvb kpx czoy." with an explanation of your method. $[10\%]$

$($c$)$ Discuss how you would improve the Vigenere cypher to make sure it implements both $[10\%]$

confusion and diffusion in the cyphertext.