Multi-user searchable encryption in the Cloud

While Searchable Encryption (SE) has been widely studied, adapting it to the multi-user setting whereby many users can upload secret les or documents and delegate search operations to multiple other users still remains an interesting problem. In this paper we show that the adversarial models used in existing multi-user searchable encryption

solutions are not realistic as they implicitly require that the cloud service provider cannot collude with some users. We then propose a stronger adversarial model, and propose a construction which is both practical and provably secure in this new model. The new solution combines the use of bilinear pairings with private information retrieval and introduces a new, non trusted entity called \proxy" to transform each user's search

query into one instance per targeted le or document.