Enhance Labeled PSI with Collision-free Hash Map

Private Set Intersection (PSI) is a cryptographic technique that takes two private sets as input and outputs their intersection to one of the participants without revealing any extra information. As a special type of PSI, labeled PSI is widely used in private web service queries. In this paper, we first describe the data expansion problem existing in the previous approaches based on cuckoo hashing. Then we present the concept of collision-free hash map, describe its ideal functionality, and give a concrete realization. Finally, we propose an enhanced labeled PSI protocol by replacing cuckoo hashing with collision-free hash map. Experiment results show that our protocol effectively solves the data expansion problem, of which the performance improves over 50% compared to the original labeled PSI protocols and over 80% compared to the mainstream privacy computing framework.