Paper 2024/725

Multi User Security of LightMAC and LightMAC_Plus

Nilanjan Datta, Institute for Advancing Intelligence, TCG CREST, Kolkata, India
Shreya Dey, Institute for Advancing Intelligence, TCG CREST, Kolkata, India, Ramakrishna Mission Vivekananda Educational and Research Institute, India
Avijit Dutta, Institute for Advancing Intelligence, TCG CREST, Kolkata, India
Devdutto Kanungo, PricewaterhouseCoopers, Kolkata, India
Abstract

In FSE'16, Luykx et al. have proposed $\textsf{LightMAC}$ that provably achieves a query length independent PRF security bound. To be precise, the construction achieves security roughly in the order of $O(q^2/2^n)$, when instantiated with two independently keyed $n$-bit block ciphers and $q$ is the total number of queries made by the adversary. Subsequently, in ASIACRYPT'17, Naito proposed a beyond-birthday-bound variant of the $\textsf{LightMAC}$ construction, dubbed as $\textsf{LightMAC_Plus}$, that is built on three independently keyed $n$-bit block ciphers and achieves $2n/3$-bits PRF security. Security analyses of these two constructions have been conducted in the single-user setting, where we assume that the adversary has the access to a single instance of the construction. In this paper, we investigate, for the first time, the security of the $\textsf{LightMAC}$ and the $\textsf{LightMAC_Plus}$ construction in the context of multi-user setting, where we assume that the adversary has access to more than one instances of the construction. In particular, we have shown that $\textsf{LightMAC}$ remains secure roughly up to $2^{n/2}$ construction queries and $2^k$ ideal-cipher queries in the ideal-cipher model and $\textsf{LightMAC_Plus}$ maintains security up to approximately $2^{2n/3}$ construction queries and $2^{2k/3}$ ideal-cipher queries in the ideal-cipher model, where $n$ denotes the block size and $k$ denotes the key size of the block cipher.

Metadata
Available format(s)
PDF
Category
Secret-key cryptography
Publication info
Preprint.
Keywords
LightMACLightMAC_PlusMulti-user SecurityMirror TheoryBeyond Birthday Bound.
Contact author(s)
nilanjan datta @ tcgcrest org
shreya dey @ tcgcrest org
avirocks dutta13 @ gmail com
kitunscool @ gmail com
History
2024-05-13: approved
2024-05-12: received
See all versions
Short URL
https://ia.cr/2024/725
License
No rights reserved
CC0

BibTeX

@misc{cryptoeprint:2024/725,
      author = {Nilanjan Datta and Shreya Dey and Avijit Dutta and Devdutto Kanungo},
      title = {Multi User Security of LightMAC and LightMAC_Plus},
      howpublished = {Cryptology ePrint Archive, Paper 2024/725},
      year = {2024},
      note = {\url{https://eprint.iacr.org/2024/725}},
      url = {https://eprint.iacr.org/2024/725}
}
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