Cyclotomic Cosets: Hidden Subgroup and Quantum Sieving Algorithm for Prime-Power Moduli
A cyclotomic quantum sieve solves CCP and related EDCP cases quickly, but not standard LWE.
The paper introduces the Cyclotomic Coset Problem, a hidden-subgroup generalization of the dihedral coset problem over prime-power cyclotomic moduli. A quantum sieve solves CCP in time and sample complexity 2 to the O_p(log n log q) with polynomial quantum space, and extends to uniform EDCP and Gaussian S|LWE in quasi-polynomial time when q is polynomial in n. The authors stress this does not by itself give a quasi-polynomial algorithm for standard LWE, because existing reductions supply too few approximate CCP states.
- CCP preserves an exact hidden-subgroup structure, unlike extrapolated DCP.
- The quantum sieve runs in 2 to the O(log n log q) time and samples.
- Uniform EDCP and Gaussian S|LWE also get quasi-polynomial time when q is polynomial.
- Authors say known reductions do not yield a quasi-polynomial attack on standard LWE.
From the original article
1 min read at arxiv.orgThe Learning With Errors (LWE) problem is a fundamental assumption in post-quantum cryptography. Regev established a quantum reduction from LWE to the Dihedral Coset Problem (DCP). Later, Brakerski et al.
By Mathias Boucher · arxiv.org
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