AES Side-Channel Countermeasure using Random Tower Field Constructions

Alexis Bonnecaze (1) , Pierre Liardet (2) , Alexandre Venelli (3)

1 IML/ERISCS et Polytech Marseille
2 LATP - Laboratoire d'Analyse, Topologie, Probabilités
3 Entreprise: Inside Secure

Masking schemes to secure AES implementations against side-channel attacks is a topic of ongoing research. The most sensitive part of the AES is the non-linear SubBytes operation, in particular, the inversion in GF(2^8), the Galois field of 2^8 elements. In hardware implementations, it is well known that the use of the tower of extensions GF(2) ⊂ GF(2^2) ⊂ GF(2^4) ⊂ GF(2^8) leads to a more efficient inversion. We propose to use a random isomorphism instead of a fixed one. Then, we study the effect of this randomization in terms of security and efficiency. Considering the field extension GF(2^8)/GF(2^4), the inverse operation leads to computation of its norm in GF(2^4). Hence, in order to thwart side-channel attack, we manage to spread the values of norms over GF(2^4). Combined with a technique of boolean masking in tower fields, our countermeasure strengthens resistance against first-order differential side-channel attacks.

Mots clés: countermeasure; composite field arithmetic; AES; masking technique; side-channel attack

Domaines: Cryptographie et sécurité [cs.CR]

Alexis Bonnecaze, Pierre Liardet, Alexandre Venelli. AES Side-Channel Countermeasure using Random Tower Field Constructions. Designs, Codes and Cryptography, 2013, 69, pp.331--349. ⟨10.1007/s10623-012-9670-x⟩. ⟨hal-00903215⟩