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 and membership text , 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.