### Efficient Leakage-Resilient MACs without Idealized Assumptions

Francesco Berti, Chun Guo, Thomas Peters, and François-Xavier Standaert

##### Abstract

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 ($\mathsf{TBC}$) that is unpredictable with leakage. This construction leverages two design twists: large tweaks for the $\mathsf{TBC}$ and a verification process that checks the inverse $\mathsf{TBC}$ 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 may incur performance overheads if specialized $\mathsf{TBC}$s with large tweaks 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 $\mathsf{TBC}$s with large tweaks and good properties for side-channel countermeasures as an interesting challenge.

Available format(s)
Category
Secret-key cryptography
Publication info
A minor revision of an IACR publication in Asiacrypt 2021
Keywords
MACleakage resilienceresistancetweakable blockcipherunpredictability
Contact author(s)
History
2021-09-20: revised
See all versions
Short URL
https://ia.cr/2021/1250

CC BY

BibTeX

@misc{cryptoeprint:2021/1250,
author = {Francesco Berti and Chun Guo and Thomas Peters and François-Xavier Standaert},
title = {Efficient Leakage-Resilient MACs  without Idealized Assumptions},
howpublished = {Cryptology ePrint Archive, Paper 2021/1250},
year = {2021},
note = {\url{https://eprint.iacr.org/2021/1250}},
url = {https://eprint.iacr.org/2021/1250}
}

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