International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Leakage Resilient Value Comparison With Application to Message Authentication

Christoph Dobraunig , Lamarr Security Research (Austria) and Graz University of Technology (Austria)
Bart Mennink , Radboud University (the Netherlands)
DOI: 10.1007/978-3-030-77886-6_13 (login may be required)
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Conference: EUROCRYPT 2021
Abstract: Side-channel attacks are a threat to secrets stored on a device, especially if an adversary has physical access to the device. As an effect of this, countermeasures against such attacks for cryptographic algorithms are a well-researched topic. In this work, we deviate from the study of cryptographic algorithms and instead focus on the side-channel protection of a much more basic operation, the comparison of a known attacker-controlled value with a secret one. Comparisons sensitive to side-channel leakage occur in tag comparisons during the verification of message authentication codes (MACs) or authenticated encryption, but are typically omitted in security analyses. Besides, also comparisons performed as part of fault countermeasures might be sensitive to side-channel attacks. In this work, we present a formal analysis on comparing values in a leakage resilient manner by utilizing cryptographic building blocks that are typically part of an implementation anyway. Our results indicate that there is no need to invest additional resources into implementing a protected comparison operation itself if a sufficiently protected implementation of a public cryptographic permutation, or a (tweakable) block cipher, is already available. We complement our contribution by applying our findings to the SuKS message authentication code used by lightweight authenticated encryption scheme ISAP, and to the classical Hash-then-PRF construction.
Video from EUROCRYPT 2021
  title={Leakage Resilient Value Comparison With Application to Message Authentication},
  author={Christoph Dobraunig and Bart Mennink},