Efficient forward secure searchable encryption supporting multi-keyword query

Searchable encryption (SE) allows client to outsource personal data to an untrusted server while protecting the data privacy, which is widely used by corporations and individuals. Recently, many works show that forward privacy is the fundamental property for secure SE cryptosystem, and several forward secure SE schemes have been proposed. However, most forward secure schemes are focus on the single-keyword query, which limit their wide application in cloud computing. In this paper, we propose an efficient forward secure searchable encryption scheme supporting multi-keyword query. Our scheme involves two new storage structures as temporary map and search tree. Specifically, when the client uploads multiple files with the same keyword, our scheme uses an encryption key to replace multiple encryption keys in the existing schemes, so that improves query efficiency. Moreover, our scheme overcomes the shortcoming that the query complexity increases linearly with the number of updated files in the existing schemes. We prove our scheme is secure with forward privacy under the random oracle model. The experimental results show that our scheme is more efficient than the existing schemes.