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On the Weakness of Non-Dual Ring-LWE Mod Prime Ideal q by Trace Map

Tomoka TAKAHASHI, Shinya OKUMURA, Atsuko MIYAJI

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Summary :

The recent decision by the National Institute of Standards and Technology (NIST) to standardize lattice-based cryptography has further increased the demand for security analysis. The Ring-Learning with Error (Ring-LWE) problem is a mathematical problem that constitutes such lattice cryptosystems. It has many algebraic properties because it is considered in the ring of integers, R, of a number field, K. These algebraic properties make the Ring-LWE based schemes efficient, although some of them are also used for attacks. When the modulus, q, is unramified in K, it is known that the Ring-LWE problem, to determine the secret information sR/qR, can be solved by determining s (mod q) ∈ Fqf for all prime ideals q lying over q. The χ2-attack determines s (mod q) ∈Fqf using chi-square tests over R/q ≅ Fqf. The χ2-attack is improved in the special case where the residue degree f is two, which is called the two-residue-degree χ2-attack. In this paper, we extend the two-residue-degree χ2-attack to the attack that works efficiently for any residue degree. As a result, the attack time against a vulnerable field using our proposed attack with parameter (q,f)=(67, 3) was 129 seconds on a standard PC. We also evaluate the vulnerability of the two-power cyclotomic fields.

Publication
IEICE TRANSACTIONS on Information Vol.E106-D No.9 pp.1423-1434
Publication Date
2023/09/01
Publicized
2023/07/13
Online ISSN
1745-1361
DOI
10.1587/transinf.2022ICP0017
Type of Manuscript
Special Section PAPER (Special Section on Information and Communication System Security)
Category

Authors

Tomoka TAKAHASHI
  Osaka University
Shinya OKUMURA
  Osaka University
Atsuko MIYAJI
  Osaka University

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