Introduction - If you have any usage issues, please Google them yourself
The inverse S-box is used in the decrypting function inv_cipher to revert the substitution
carried out via the S-box.
The corresponding AES-Matlab function declared in Line 1 of Listing 7 takes the Sbox
(s_box) as its input and generates the inverse S-box inv_s_box in a single loop
. The loop runs through all elements of the S-box, interprets the current
S-box element value as an index into the inverse S-box and inserts the values 0 . . . 255
at the appropriate places in the inverse S-box