Mutual Information Analysis

Abstract

We propose a generic information-theoretic distinguisher for differential side-channel analysis. Our model of side-channel leakage is a refinement of the one given by Standaert et al. An embedded device containing a secret key is modeled as a black box with a leakage function whose output is captured by an adversary through the noisy measure- ment of a physical observable. Although quite general, the model and the distinguisher are practical and allow us to develop a new differen- tial side-channel attack.More precisely, we build a distinguisher that uses the value of theMutual Information between the observed measurements and a hypothetical leakage to rank key guesses. The attack is effective without any knowledge about the particular dependencies between mea- surements and leakage as well as between leakage and processed data, which makes it a universal tool. Our approach is confirmed by results of power analysis experiments. We demonstrate that the model and the attack work effectively in an attack scenario against DPA-resistant logic.