Outsourced private set intersection using homomorphic encryption

Abstract

Private set intersection enables two parties -- a client and a server -- to compute the intersection of their respective sets without disclosing anything else. It is a fundamental operation -- equivalent to a secure, distributed database join -- and has many applications particularly in privacy-preserving law enforcement. In this paper we present a novel protocol that has linear complexity, is secure in the malicious model without random oracles, is client set size-independent and efficient. Furthermore, the computation of the intersection can be outsourced to an oblivious service provider, as in secure cloud computing. We leverage a completely novel construction for computing the intersection using Bloom filter and homomorphic encryption. For outsourcing we require and introduce a new homomorphic encryption scheme which may be of independent interest.