Paper 2024/1712 Original: eprint.iacr.org/2024/1712 ↗

Efficient Updatable PSI from Asymmetric PSI and PSU

Abstract

Private Set Intersection (PSI) allows two mutually untrusted parties to compute the intersection of their private sets without revealing additional information. In general, PSI operates in a static setting, where the computation is performed only once on the input sets of both parties. Badrinarayanan et al. initiated the study of Updatable PSI (UPSI), which extends this capability to dynamically updating sets, enabling both parties to securely compute the intersection as their sets are modified while incurring significantly less overhead than re-executing a conventional PSI. However, existing UPSI protocols either do not support arbitrary deletion of elements or incur high computational and communication overhead. This work combines asymmetric PSI with Private Set Union (PSU) to present a novel UPSI protocol, which supports arbitrary additions and deletions of elements, offering a flexible approach to update sets. Furthermore, our protocol enjoys efficient performance compared to previous work. Specifically, we implement our protocol and compare it against state-of-the-art conventional PSI and UPSI protocols. Experimental results demonstrate that our UPSI protocol achieves up to three orders of magnitude reduction in computational overhead and incurs $190 \sim 707 \times$ less communication overhead than the state-of-the-art UPSI protocol that supports arbitrary additions and deletions. Our implementation is available at: \url{https://github.com/ShallMate/upsi}.