Description
SQIsign is an isogeny-based signature scheme which has recently advanced to round 2 of NIST's call for additional post-quantum signatures. A central operation in SQIsign is lattice reduction of special full-rank lattices in dimension 4. As these input lattices are secret, this computation must be protected against side-channel attacks. However, known lattice reduction algorithms like the famous LLL algorithm are not naturally constant-time.
This talk presents a new, constant-time lattice reduction algorithm, developed in collaboration with Ottó Hanyecz, Alexander Karenin, Elena Kirshanova and Péter Kutas. We first give a short introduction to SQIsign without detailing its inner workings. Then, we analyze different existing lattice reduction algorithms, and present our constant-time version, which is based on the BKZ-2 algorithm. Finally, we explain some implementation choices and discuss the performance using two sets of parameters: one for provable guarantees on its output, and one for speed with a reasonable success rate.
Eprint: https://eprint.iacr.org/2025/027
Practical infos
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Endomorphisms via Splittings
Speaker : Min-Yi Shen - No Affiliation
One of the fundamental hardness assumptions underlying isogeny-based cryptography is the problem of finding a non-trivial endomorphism of a given supersingular elliptic curve. In this talk, we show that the problem is related to the problem of finding a splitting of a principally polarised superspecial abelian surface. In particular, we provide formal security reductions and a proof-of-concept[…]-
Cryptography
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