Lightweight Threshold Private Set Intersection via Oblivious Transfer

Abstract

As a significant basis for privacy-preserving applications of Secure Multiparty Computation (MPC), Private Set Intersection (PSI) has long been a question of great interest in a wide range of field, such as ad conversion rates and private contact tracing. Threshold PSI (\(t\)-\(\mathsf {PSI}\)), a variant of PSI, allows two parties to learn the intersection of two sets only if the cardinality of intersection is larger (or lesser) than a threshold t. In this paper, we give a generic \(t\)-\(\mathsf {PSI}\) construction that relies heavily on Oblivious Transfer (OT). Without resorting to the relatively expensive homomorphic calculation approaches from public-key mechanism, two kinds of \(t\)-\(\mathsf {PSI}\) protocols could be efficiently implemented based on our proposed construction, i.e., \(t^{\scriptscriptstyle {\le }}\mathsf {PSI}\) and \(t^{\scriptscriptstyle {>}}\text {-}\mathsf {PSI}\). Specially, we construct two efficient protocols named secret-sharing private equality test Open image in new window and membership text Open image in new window , which enable PSI to scale to a wide range of practical applications. The experimental simulation results show that our protocols are efficient and computation friendly.