On the Optimality of Differential Fault Analyses on CLEFIA

Differential Fault Analysis is a powerful cryptanalytic tool to reveal secret keys of cryptographic algorithms. By corrupting the computation of an algorithm, an attacker gets additional information about the secret key. In 2012, several Differential Fault Analyses on the AES cipher were analyzed from an informationtheoretic perspective. This analysis exposed whether or not the leaked information was fully exploited. It revealed if an analysis was already optimal or if it could still be improved. We applied the same approach to all existing Differential Fault Analyses on the CLEFIA cipher. We show that only some of these attacks are already optimal. We improve those analyses which did not exploit all information. With one exception, all attacks against CLEFIA-128 reach the theoretical limit after our improvement. Our improvement of an attack against CLEFIA-192 and CLEFIA-256 reduces the number of fault injections to the lowest possible number reached to date.