TY - JOUR
AU - Grassi, Lorenzo
PY - 2018/06/07
Y2 - 2024/04/25
TI - Mixture Differential Cryptanalysis: a New Approach to Distinguishers and Attacks on round-reduced AES
JF - IACR Transactions on Symmetric Cryptology
JA - ToSC
VL - 2018
IS - 2
SE - Articles
DO - 10.13154/tosc.v2018.i2.133-160
UR - https://tosc.iacr.org/index.php/ToSC/article/view/891
SP - 133-160
AB - <p>At Eurocrypt 2017 the first secret-key distinguisher for 5-round AES - based on the “multiple-of-8” property - has been presented. Although it allows to distinguish a random permutation from an AES-like one, it seems rather hard to implement a key-recovery attack different than brute-force like using such a distinguisher. In this paper we introduce “<em>Mixture Differential Cryptanalysis</em>” on round-reduced AESlike ciphers, a way to translate the (complex) “multiple-of-8” 5-round distinguisher into a simpler and more convenient one (though, on a smaller number of rounds). Given a pair of chosen plaintexts, the idea is to construct new pairs of plaintexts by <em>mixing</em> the generating variables of the original pair of plaintexts. Here we theoretically prove that for 4-round AES the corresponding ciphertexts of the original pair of plaintexts lie in a particular subspace if and only if the corresponding pairs of ciphertexts of the new pairs of plaintexts have the same property. Such secret-key distinguisher - which is independent of the secret-key, of the details of the S-Box and of the MixColumns matrix (except for the branch number equal to 5) - can be used as starting point to set up new key-recovery attacks on round-reduced AES. Besides a theoretical explanation, we also provide a practical verification both of the distinguisher and of the attack.</p>
ER -