Forward and Backward Private Dynamic Searchable Encryption with Better Space Efficiency

Abstract

Dynamic searchable symmetric encryption (SSE) provides efficient update and search operations over encrypted data, while it leaks some inconsequential information to increase search efficiency. Since the more dynamic SSE allows leakage, the easier it is to break its security, it is important to realize efficient schemes with less leakages. For that reason, most recent works on dynamic SSE focus on forward and backward privacy, which are important security notions for dynamic SSE. In particular, Sun et al. (NDSS 2021) recently proposed Aura, an efficient dynamic SSE scheme with forward and backward privacy. Although Aura provides good update and search efficiency, it requires large encrypted database. Taking into account the practical use of dynamic SSE, i.e., search systems that many users involve, the sizes of encrypted databases should be small enough. In this paper, based on Aura, we propose a new dynamic SSE scheme with forward and backward privacy, called Aura +; it provides not only efficient update and search operations but also smaller encrypted database than Aura, though Aura+ requires a few more interactions than Aura.