Paper 2023/1198

Towards Achieving Provable Side-Channel Security in Practice

Abstract

Physical side-channel attacks are powerful attacks that exploit a device's physical emanations to break the security of cryptographic implementations. Many countermeasures have been proposed against these attacks, especially the widely-used and efficient masking countermeasure. Nevertheless, proving the security of masked implementations is challenging. Current techniques rely on empirical approaches to validate the security of such implementations. On the other hand, the theoretical community introduced leakage models to provide formal proofs of the security of masked implementations. Meanwhile, these leakage models rely on physical assumptions that are difficult to satisfy in practice, and the literature lacks a clear framework to implement proven secure constructions on a physical device while preserving the proven security. In this paper, we present a complete methodology describing the steps to turn an abstract masking scheme proven secure in a theoretical leakage model into a physical implementation satisfying provable security against side-channel attacks in practice. We propose new tools to enforce or relax the physical assumptions the indeal noisy leakage model rely on and provide novel ways of including them in a physical implementation. We also highlight the design goals for an embedded device to reach high levels of proven security, discussing the limitations and open problems of the practical usability of the leakage models. Our goal is to show that it is possible to bridge theory and practice and to motivate further research to fully close the gap and get practical implementations proven secure against side-channel attacks on a physical device without any ideal assumption about the leakage.