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Mind the Bad Norms: Revisiting Compressed Oracle-based Quantum Indistinguishability Proofs
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| Conference: | ASIACRYPT 2024 |
| Abstract: | In this work, we revisit the Hosoyamada-Iwata (HI) proof for the quantum CPA security of the 4-round Luby-Rackoff construction and identify a gap that appears to undermine the security proof. We emphasize that this is not an attack, and the construction may still achieve the claimed security level. However, this gap raises concerns about the feasibility of establishing a formal security proof for the 4-round Luby-Rackoff construction. In fact, the issue persists even if the number of rounds is increased arbitrarily. On a positive note, we restore the security of the 4-round Luby-Rackoff construction in the non-adaptive setting, achieving security up to $2^{n/6}$ superposition queries. Furthermore, we establish the quantum CPA security of the 4-round MistyR and 5-round MistyL constructions, up to $2^{n/5}$ and $2^{n/7}$ superposition queries, respectively, where $n$ denotes the size of the underlying permutation. |
BibTeX
@inproceedings{asiacrypt-2024-34750,
title={Mind the Bad Norms: Revisiting Compressed Oracle-based Quantum Indistinguishability Proofs},
publisher={Springer-Verlag},
author={Ritam Bhaumik and Benoît Cogliati and Jordan Ethan and Ashwin Jha},
year=2024
}