DMPSI: Efficient Scalable Delegated Multiparty PSI and PSI-CA with Oblivious PRF

Multiparty private set intersection (PSI) allows several parties, each holding a set of elements, to jointly compute the intersection without leaking any additional information. With the development of cloud computing, delegating the computation to an untrsuted cloud server is becoming a major problem, where the untrusted cloud server may try to get some sensitive information from clients' private information. However, it is complex to build an efficient and reliable scheme to protect user privacy. In order to overcome this problem, we propose DMPSI, an efficient delegated PSI (with cardinality) protocol in a multiparty setting. DMPSI avoids using heavy cryptographic primitives (mainly rely on symmetric-key encryption) to achieve better performance. In addition, both PSI and PSI with the cardinality of DMPSI are secure against semi-honest adversaries and allow any number of colluding clients (at least one honest client). We do experiments to compare the proposed DMPSI with some state-of-the-art works to evaluate overall performance. In addition, we also compare the proposed Oks-PRF with some state-of-the-art multi-point OPRF to highlight our efficiency. The experimental results show that proposed both Oks-PRF and DMPSI(-CA) has better performance and is scalable in the number of clients and the set size.