(100 points) Write a program that performs encryption and decryption using Hill Cipher. You can assume that the matrix key is 2X2. Your program MUST check validity of the KEY!You can assume that the ciphertext is a string of UPPER CASE letters and the plaintext is the string of LOWER CASE letters.

You can assume that there are no other characters in the input strings.

Test your program on the following examples: Input/Output Test

Reduce Complexity Option (75 points) - Answer Input/Output Test questions performing calculations by hand.