Faster unbalanced Private Set Intersection in the semi-honest setting

Abstract

Protocols for Private Set Intersection (PSI) are important cryptographic techniques to perform joint operations on datasets in a privacy-preserving way. They allow two parties to compute the intersection of their private sets without revealing any additional information beyond the intersection itself, for one party (one-way) or both parties (mutual). Despite the several PSI protocols available in the literature, only recently techniques have been applied to existing PSI protocols in order to make them more efficient when one of the parties holds a set much smaller than the other. This is a realistic scenario in many cases, characterizing the unbalanced setting. Thus, this paper builds on modern cryptographic engineering techniques and proposes optimizations for a promising one-way PSI protocol based on public-key cryptography secure against semi-honest adversaries. We show that our improvements and optimizations yield a protocol that outperforms the communication complexity and the run time of previous proposals in the unbalanced setting.