## CryptoDB

### Paper: Efficient Leakage-Resilient MACs without Idealized Assumptions

Authors: Francesco Berti , Darmstadt University, Germany Chun Guo , Shandong University, China Thomas Peters , UCLouvain, Belgium François-Xavier Standaert , UCLouvain, Belgium DOI: 10.1007/978-3-030-92075-3_4 Search ePrint Search Google Slides ASIACRYPT 2021 The security proofs of leakage-resilient MACs based on symmetric building blocks currently rely on idealized assumptions that hardly translate into interpretable guidelines for the cryptographic engineers implementing these schemes. In this paper, we first present a leakage-resilient MAC that is both efficient and secure under standard and easily interpretable black box and physical assumptions. It only requires a collision resistant hash function and a single call per message authentication to a Tweakable Block Cipher (TBC) that is unpredictable with leakage. This construction leverages two design twists: large tweaks for the TBC and a verification process that checks the inverse TBC against a constant. It enjoys beyond birthday security bounds. We then discuss the cost of getting rid of these design twists. We show that security can be proven without them as well. Yet, a construction without large tweaks requires stronger (non idealized) assumptions and inevitably incurs performance overheads if specialized TBCs can be exploited, and a construction without twisted verification requires even stronger assumptions (still non idealized) and leads to more involved bounds. The combination of these results makes a case for our first pragmatic construction and suggests the design of TBCs with large tweaks and good properties for side-channel countermeasures as an interesting challenge.
##### BibTeX
@inproceedings{asiacrypt-2021-31479,
title={Efficient Leakage-Resilient MACs without Idealized Assumptions},
publisher={Springer-Verlag},
doi={10.1007/978-3-030-92075-3_4},
author={Francesco Berti and Chun Guo and Thomas Peters and François-Xavier Standaert},
year=2021
}