Forward Private Searchable Encryption with Conjunctive Keywords Query

Abstract

Dynamic searchable symmetric encryption (DSSE) allows addition and deletion operation on an encrypted database. Recently, several attack works (such as IKK) show that existing SSE definition which leaks access pattern and search pattern cannot capture the adversary in the real world. These works underline the necessity for forward privacy. To achieve forward privacy, updating search token is considered as a simple yet efficient method. In this paper, we concentrate on scenario of updating a batch of files containing the same keyword and propose an efficient forward private searchable encryption (EFSE) scheme with a novel batch update. In this scenario, by batch update method, the search token corresponding to the keyword only needs to be updated once. Then for each file in the batch, we use updated search token combining number of this file in the batch to transform the pair (file, keyword) into encrypted index. In the scenario mentioned above, the number of updating search token operation in our EFSE is 1, while the one in existing forward private searchable encryption scheme based on updating search token is the size of batch. In addition, by integrating Cash’s OXT scheme, we extend our EFSE scheme to support conjunctive keywords query. Finally, we give the rigorous security analysis for our proposed two schemes and give performance evaluation for the basic one.