One for all: Efficient verifiable dynamic multi-user searchable encryption in the presence of corrupted users

Abstract

Dynamic multi-user searchable symmetric encryption (DMUSSE) enables the data owner to dynamically outsource encrypted database to the cloud server and selectively share the search capability with data users. However, inter-user state synchronization is expensive but often necessary in multi-user setting. In addition, only a few works are proposed against the malicious servers that achieve verifiability (guarantee the integrity of query results) by deploying a Merkle tree for all database entries in a straightforward way, which is inevitably subject to logarithmic communication overhead. In this work, we propose a new verifiable DMUSSE scheme with improved performance, while maintaining user-server collusion resistance. Concretely, we first design an efficient and forward-and-backward-secure DMUSSE scheme with the aid of Hyperledger Fabric (a permissioned blockchain), greatly reducing synchronous communication and computation. In particular, our scheme does not reveal any information about uncorrupted users when corrupted users collude with an adversarial server. Then, we achieve efficient verifiability of query results based on multiset hash functions with O(1) communication cost. Finally, we compare our scheme with the state-of-the-art solutions O-μSE and Q-μSE (Chamani et al. TDSC 2021). Experimental results show that our scheme brings at least 90.9% communication savings, 2.75×, 109.2×, and 11.67× speedup in search, update, and verify time, respectively.