Using Subspace-Based Template Attacks to Compare and Combine Power and Electromagnetic Information Leakages

The power consumption and electromagnetic radiation are among the most extensively used side-channels for analyzing physically observable cryptographic devices. This paper tackles three important questions in this respect. First, we compare the effectiveness of these two side-channels. We investigate the common belief that electromagnetic leakages lead to more powerful attacks than their power consumption counterpart. Second we study the best combination of the power and electromagnetic leakages. A quantified analysis based on sound information theoretic and security metrics is provided for these purposes. Third, we evaluate the effectiveness of two data dimensionality reduction techniques for constructing subspace-based template attacks. Selecting automatically the meaningful time samples in side-channel leakage traces is an important problem in the application of template attacks and it usually relies on heuristics. We show how classical statistical tools such as Principal Component Analysis and Fisher Linear Discriminant Analysis can be used for efficiently preprocessing the leakage traces.