2024/10/01 by Joonas Ahola, Iván Blanco-Chacón, Ahola, Joonas +9
Computer Science · Mathematics · #11T71 (Primary) #94A60 (Secondary) #Algebraic Geometry and Number Theory #Cryptography and Security (cs.CR) #FOS: Computer and information sciences #FOS: Mathematics #Number Theory (math.NT) #Polynomial and algebraic computation #Rings, Modules, and Algebras
paper · pdf · doi:10.48550/arxiv.2410.00792
openalex publication_date 2024/10/01 · openalex created_date 2024/10/29 · openalex updated_date 2026/07/28
We prove the equivalence between the Ring Learning With Errors (RLWE) and the Polynomial Learning With Errors (PLWE) problems for the maximal totally real subfield of the 2r 3s-th cyclotomic field for r ≥ 3 and s ≥ 1. Moreover, we describe a fast algorithm for computing the product of two elements in the ring of integers of these subfields. This multiplication algorithm has quasilinear complexity in the dimension of the field, as it makes use of the fast Discrete Cosine Transform (DCT). Our approach assumes that the two input polynomials are given in a basis of Chebyshev-like polynomials, in contrast to the customary power basis. To validate this assumption, we prove that the change of basis from the power basis to the Chebyshev-like basis can be computed with O(n log n) arithmetic operations, where n is the problem dimension. Finally, we provide a heuristic and theoretical comparison of the vulnerability to some attacks for the p-th cyclotomic field versus the maximal totally real subextension of the 4p-th cyclotomic field for a reasonable set of parameters of cryptographic size.