MixColumns Properties and Attacks on (round-reduced) AES with a Single Secret S-Box

In this paper, we present new key-recovery attacks on AES with a single secret S-Box. Several attacks for this model have been proposed in literature, the most recent ones at Crypto’16 and FSE’17. Both these attacks exploit a particular property of the MixColumns matrix to recover the secret-key. In this work, we show that the same attacks work exploiting a weaker property of the MixColumns matrix. As first result, this allows to (largely) increase the number of MixColumns matrices for which it is possible to set up all these attacks. As a second result, we present new attacks on 5round AES with a single secret S-Box that exploit the new multiple-of-n property recently proposed at Eurocrypt’17. This property is based on the fact that choosing a particular set of plaintexts, the number of pairs of ciphertexts that lie in a particular subspace is a multiple of n.