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research article

An Efficient Threshold Access-Structure for RLWE-Based Multiparty Homomorphic Encryption

Mouchet, Christian  
•
Bertrand, Elliott
•
Hubaux, Jean-Pierre  
April 1, 2023
Journal Of Cryptology

We propose and implement a multiparty homomorphic encryption (MHE) scheme with a t-out-of -N-threshold access-structure that is efficient and does not require a trusted dealer in the common random string model. We construct this scheme from the ring-learning-with-error assumptions and as an extension of the MHE scheme of Mouchet et al. (PETS 21). By means of a specially adapted share re-sharing procedure, this extension can be used to relax the N-out-of -N-threshold access-structure of the original scheme into a t-out-of -N-threshold one. This procedure introduces only a single round of communication during the setup phase, after which any set of at least t parties can compute a t-out-of -t additive sharing of the secret-key with no interaction; this new sharing can be used directly in the scheme of Mouchet et al. We show that, by performing Shamir re-sharing over the MHE ciphertext-space ring with a carefully chosen exceptional set, this reconstruction procedure can be made secure and has negligible overhead. Moreover, it only requires the parties to store a constant-size state after its setup phase. Hence, in addition to fault tolerance, lowering the corruption threshold also yields considerable efficiency benefits, by enabling the distribution of batched secret-key operations among the online parties. We implemented and open-sourced our scheme in the Lattigo library.

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Type
research article
DOI
10.1007/s00145-023-09452-8
Web of Science ID

WOS:000957186800002

Author(s)
Mouchet, Christian  
Bertrand, Elliott
Hubaux, Jean-Pierre  
Date Issued

2023-04-01

Publisher

SPRINGER

Published in
Journal Of Cryptology
Volume

36

Issue

2

Start page

10

Subjects

Computer Science, Theory & Methods

•

Engineering, Electrical & Electronic

•

Mathematics, Applied

•

Computer Science

•

Engineering

•

Mathematics

•

multiparty homomorphic encryption

•

threshold access-structures

•

secure multiparty computation

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

Available on Infoscience
April 24, 2023
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/197048
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