A Central Limit Approach for Ring-LWE Noise Analysis

Sean Murphy; Rachel Player

doi:10.62056/ay76c0kr

A Central Limit Approach for Ring-LWE Noise Analysis

Authors

Sean Murphy, Rachel Player

Sean Murphy

Royal Holloway, University of London, Egham, UK
s dot murphy at rhul dot ac dot uk

Rachel Player

Royal Holloway, University of London, Egham, UK
rachel dot player at rhul dot ac dot uk

Keywords: Ring-LWE Central Limit Theorem decryption failure probability BGV scheme homomorphic encryption

Abstract

This paper develops Central Limit arguments for analysing the noise in ciphertexts in two homomorphic encryption schemes that are based on Ring-LWE. The first main contribution of this paper is to present and evaluate an average-case noise analysis for the BGV scheme. Our approach relies on the recent work of Costache et al.(SAC 2023) that gives the approximation of a polynomial product as a multivariate Normal distribution. We show how this result can be applied in the BGV context and evaluate its efficacy. We find this average-case approach can much more closely model the noise growth in BGV implementations than prior approaches, but in some cases it can also underestimate the practical noise growth. Our second main contribution is to develop a Central Limit framework to analyse the noise growth in the homomorphic Ring-LWE cryptosystem of Lyubashevsky, Peikert and Regev (Eurocrypt 2013, full version). Our approach is very general: apart from finite variance, no assumption on the distribution of the noise is required (in particular, the noise need not be subgaussian). We show that our approach leads to tighter bounds for the probability of decryption failure than those of prior work.

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DOI: https://doi.org/10.62056/ay76c0kr

History

Submitted: 2024-03-20
Accepted: 2024-06-03
Published: 2024-07-08

How to cite

Sean Murphy and Rachel Player, "A Central Limit Approach for Ring-LWE Noise Analysis," IACR Communications in Cryptology, vol. 1, no. 2, Jul 08, 2024, doi: 10.62056/ay76c0kr.

License

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This work is licensed under a Creative Commons Attribution (CC BY) license.

@article{CiC-1-2-7,
    author = "Murphy, Sean and Player, Rachel",
    journal = "{IACR} {C}ommunications in {C}ryptology",
    publisher = "{I}nternational {A}ssociation for {C}ryptologic {R}esearch",
    title = "A Central Limit Approach for Ring-{LWE} Noise Analysis",
    volume = "1",
    number = "2",
    date = "2024-07-08",
    year = "2024",
    issn = "3006-5496",
    doi = "10.62056/ay76c0kr"
}

TY - JOUR
AU - Murphy, Sean
AU - Player, Rachel
PY  - 2024
TI  - A Central Limit Approach for Ring-LWE Noise Analysis
JF  - IACR Communications in Cryptology
JA  - CIC
VL  - 1
IS  - 2
DO  - 10.62056/ay76c0kr
UR  - https://doi.org/10.62056/ay76c0kr
AB  - <p>This paper develops Central Limit arguments for analysing the noise in ciphertexts in two homomorphic encryption schemes that are based on Ring-LWE. The first main contribution of this paper is to present and evaluate an average-case noise analysis for the BGV scheme. Our approach relies on the recent work of Costache et al.(SAC 2023) that gives the approximation of a polynomial product as a multivariate Normal distribution. We show how this result can be applied in the BGV context and evaluate its efficacy. We find this average-case approach can much more closely model the noise growth in BGV implementations than prior approaches, but in some cases it can also underestimate the practical noise growth. Our second main contribution is to develop a Central Limit framework to analyse the noise growth in the homomorphic Ring-LWE cryptosystem of Lyubashevsky, Peikert and Regev (Eurocrypt 2013, full version). Our approach is very general: apart from finite variance, no assumption on the distribution of the noise is required (in particular, the noise need not be subgaussian). We show that our approach leads to tighter bounds for the probability of decryption failure than those of prior work. </p>
ER  -

Sean Murphy and Rachel Player, "A Central Limit Approach for Ring-LWE Noise Analysis," IACR Communications in Cryptology, vol. 1, no. 2, Jul 08, 2024, doi: 10.62056/ay76c0kr.