Outsourced Private Set Intersection: Primitives, Properties, and Future Directions

Abstract.  Outsourced private set intersection (PSI), also known as delegated, server-aided, or cloud-assisted PSI, refers to the setting where parties delegate the required computation, and sometimes storage, to an untrusted (cloud) server.  In this talk, we provide an overview of the outsourced PSI landscape, categorizing the different cryptographic primitives and introducing our framework for understanding the key properties that distinguish these protocols, including cardinality leakage, repeatability, authorization, verifiability, updatability, and collusion assumptions.  Using this framework, we will further discuss the factors that influence protocol selection in practice, and present our interactive tool designed to help developers identify schemes that best match their requirements.  Finally, we highlight gaps between recent advances in traditional PSI and the current state of outsourced PSI as promising future research directions.

Joint work: Sophie Hawkes, Christian Weinert.

Suggested readings

• SoK: Outsourced Private Set Intersection (ia.cr/2026/080)