Cryptology ePrint Archive: Report 2021/402
Leakage Resilient Value Comparison With Application to Message Authentication
Christoph Dobraunig and Bart Mennink
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.
Category / Keywords: leakage resilience, value comparison, tag verification
Original Publication (with minor differences): IACR-EUROCRYPT-2021
Date: received 25 Mar 2021
Contact author: christoph dobraunig at lamarr at, b mennink@cs ru nl
Available format(s): PDF | BibTeX Citation
Version: 20210327:071742 (All versions of this report)
Short URL: ia.cr/2021/402
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