Cryptography Teacher Interview Question:

Is the following matrix the inverse matrix of the matrix used in the mix columns step?
x3 + 1 x
x x3 + 1

a) Yes
b) No
c) Can't say
d) Insufficient Information

Submitted by: Muhammad

a) Yes
Explanation: On multiplying this matrix with the mix columns matrix we get the identity matrix, this proves that it is an inverse matrix.
Submitted by: Muhammad