# Active S-boxes for AES with 8x8 MDS matrix

One way to enhance the security of AES is by increasing the number of active S-boxes. Larger MDS matrices are used to increase the number of active S-boxes. Using a $$4\times4$$ MDS matrix results in 25 active S-boxes after 4 rounds.

How many S-boxes would be active after 4 rounds using an $$8\times8$$ MDS matrix?

• without actually doing the math, I would say 49? Mar 1 '16 at 10:37
• Thank you for the answer. could you please show the math? Mar 2 '16 at 9:19
• It may depend on how you arrange the two matrices, since they interact with shift rows. Sep 3 '20 at 13:27