Fast two-server multi-user searchable encryption with strict access pattern leakage

Abstract

A recent paper showed that most Multi-User Searchable Encryption protocols do not provide any privacy without the assumption that all users can be trusted, an assumption too strong to be realistic for a MUSE system. As to the few MUSE protocols that are not affected, they all suffer from some scalability issues. We present the first MUSE protocol that does protect against user-server collusions, and yet scales very well. The protocol is also very simple. We prove that the leakage of the protocol is limited to the access pattern of queries and we report on performance measurements from a proof-of-concept implementation.