Impossible differential attacks against Rijndael and Crypton have been proposed up to 5-round. In this paper we expand the
impossible differential attacks to 6-round. Although we use the same 4-round impossible differential as in five round attacks,
we put this impossible differential in the middle of 6-round. That is, we will consider one round before the impossible differential
and one more round after. The complexity of the proposed attack is bigger than that of the Square attack, but still less than
that of the exhaustive search.