ARIA — Why Have One S-Box, When You Can Have Two?

ARIA was designed in 2003 is a block cipher. It uses substitution (S-box) and permutation (P-box) network structure based on AES. As with AES it uses a 128-bit block size, and key sizes of 128 (12 rounds), 192 (14 rounds), or 256 bits (16 rounds). It differs from AES in that it uses two 8×8-bit S-boxes and their inverses for each of the alternate rounds (whereas AES only uses one set of S-boxes).

A core strength of AES (Rijndael) is the usage of the S-box and where we scramble bytes through the encryption process, and then unscramble them for decryption. With AES we use a 128-bit block and which has 16 bytes, and where we have a number of rounds. With a 128-bit key we have 10 rounds, a 192-bit key has 12 rounds and a 256-bit key has 14 rounds. The following outlines the process:

But some worry about the strength of the S-box in AES, and if it were to be cracked, it may open-up encrypted data. Some companies have thus been looking for an alternative.

Demo: here.

ARIA uses two S-boxes. One of these is: