In Rijndael cipher, there is a process named “Mix Column”. The process is actually matrix multiplication over GF(28). Mathematically speaking it is defined as:
But wait, how to do this in reality. I meant, how to implement mix-column in combinational logic. I was wondering that question also. Finally i spent several hours to draw mix-column process on logic gates. It was a tedious job, but no matters, jut to satisfy ourself. The picture is below, just click it to see full-sized one (warning extra large picture)😀
Since the basic process of mix column is multiplication over GF(28). You can understand the concept of this application by extending my previous post about finite field multiplication of Rijndael cipher. Hopefully this piece benefit you anyway ;p .