Paper 2019/343

Optimizations of Side-Channel Attack on AES MixColumns Using Chosen Input

Aurelien Vasselle and Antoine Wurcker

Abstract

Considering AES sub-steps that can be attacked with a small guess space, the most practicable is to target SubBytes of extremal rounds. For its contrast between candidates (non-linearity) and that the search space is reduced to 28 -sized blocks. But when such point of interests are not available, MixColumns may be considered but involve search spaces of 2^32 -sized blocks. This number of attacks to run being often considered as unrealistic to reach, published papers propose to attack using chosen inputs in order to reduce back search space to 2^8 -sized blocks. Several sets of chosen inputs acquisition will then be required to succeed an attack. Our contribution consists in an optimization of usage of gained information that allows to drastically reduce the number of set needed to realize such an attack, even to only one set in some configurations.