A Fast Multiplication Algorithm and RLWE-PLWE Equivalence for the Maximal Real Subfield of the $2^r p^s$-th Cyclotomic Field

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Main Authors: Bolaños, Wilmar, Haavikko, Antti, Sánchez-Ledesma, Rodrigo Martín
Format: Preprint
Published: 2025
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author Bolaños, Wilmar
Haavikko, Antti
Sánchez-Ledesma, Rodrigo Martín
author_facet Bolaños, Wilmar
Haavikko, Antti
Sánchez-Ledesma, Rodrigo Martín
contents This paper proves the RLWE-PLWE equivalence for the maximal real subfields of the cyclotomic fields with conductor $n = 2^r p^s$, where $p$ is an odd prime, and $r \geq 0$ and $s \geq 1$ are integers. In particular, we show that the canonical embedding as a linear transform has a condition number bounded above by a polynomial in $n$. In addition, we describe a fast multiplication algorithm in the ring of integers of these real subfields. The multiplication algorithm uses the fast Discrete Cosine Transform (DCT) and has computational complexity $\mathcal{O}(n \log n)$. Both the proof of the RLWE-PLWE equivalence and the fast multiplication algorithm are generalizations of previous results by Ahola et al., where the same claims are proved for a single prime $p = 3$.
format Preprint
id arxiv_https___arxiv_org_abs_2504_05159
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Fast Multiplication Algorithm and RLWE-PLWE Equivalence for the Maximal Real Subfield of the $2^r p^s$-th Cyclotomic Field
Bolaños, Wilmar
Haavikko, Antti
Sánchez-Ledesma, Rodrigo Martín
Cryptography and Security
Number Theory
94A60 (Primary), 11R80, 11T06 (Secondary)
E.3.3
This paper proves the RLWE-PLWE equivalence for the maximal real subfields of the cyclotomic fields with conductor $n = 2^r p^s$, where $p$ is an odd prime, and $r \geq 0$ and $s \geq 1$ are integers. In particular, we show that the canonical embedding as a linear transform has a condition number bounded above by a polynomial in $n$. In addition, we describe a fast multiplication algorithm in the ring of integers of these real subfields. The multiplication algorithm uses the fast Discrete Cosine Transform (DCT) and has computational complexity $\mathcal{O}(n \log n)$. Both the proof of the RLWE-PLWE equivalence and the fast multiplication algorithm are generalizations of previous results by Ahola et al., where the same claims are proved for a single prime $p = 3$.
title A Fast Multiplication Algorithm and RLWE-PLWE Equivalence for the Maximal Real Subfield of the $2^r p^s$-th Cyclotomic Field
topic Cryptography and Security
Number Theory
94A60 (Primary), 11R80, 11T06 (Secondary)
E.3.3
url https://arxiv.org/abs/2504.05159