A Note on the Security Framework of Two-key DbHtS MACs

Tingting Guo; Peng Wang

Paper 2022/375

A Note on the Security Framework of Two-key DbHtS MACs

Tingting Guo and Peng Wang

Abstract

Double-block Hash-then-Sum (DbHtS) MACs are a class of MACs achieve beyond-birthday-bound (BBB) security, including SUM-ECBC, PMAC_Plus, 3kf9 and LightMAC_Plus etc. Recently, Shen et al. (Crypto 2021) proposed a security framework for two-key DbHtS MACs in the multi-user setting, stating that when the underlying blockcipher is ideal and the universal hash function is regular and almost universal, the two-key DbHtS MACs achieve 2n/3-bit security. Unfortunately, the regular and universal properties can not guarantee the BBB security of two-key DbHtS MACs. We propose three counter-examples which are proved to be 2n/3-bit secure in the multi-user setting by the framework, but can be broken with probability 1 using only O(2^{n/2}) queries even in the single-user setting. We also point out the miscalculation in their proof leading to such a flaw. However, we haven’t found attacks against 2k-SUM-ECBC, 2k-PMAC_Plus and 2k-LightMAC_Plus proved 2n/3-bit security in their paper.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Preprint. MINOR revision.
Keywords: MAC DbHtS Beyond-birthday-bound security Multi-user security
Contact author(s): guotingting @ iie ac cn
w rocking @ gmail com
History: 2022-04-17: last of 8 revisions; 2022-03-22: received; See all versions
Short URL: https://ia.cr/2022/375
License: CC BY

BibTeX

@misc{cryptoeprint:2022/375,
      author = {Tingting Guo and Peng Wang},
      title = {A Note on the Security Framework of Two-key DbHtS MACs},
      howpublished = {Cryptology ePrint Archive, Paper 2022/375},
      year = {2022},
      note = {\url{https://eprint.iacr.org/2022/375}},
      url = {https://eprint.iacr.org/2022/375}
}