Verifiable multi-client blockchain-based dynamic data retrieval

Blockchain-based verifiable dynamic searchable symmetric encryption (BV-DSSE) enables users to retrieve data efficiently and publicly verify results in data-updatable decentralized storage scenarios. However, the existing BV-DSSE schemes have to store larger data structures on the blockchain to complete the result verification, which makes the computation and storage overhead on the chain substantial. In addition, to enhance data utilization and ensure privacy retrieval, a multi-client revocable BV-DSSE has been proposed that can revoke access rights for malicious users. However, existing solutions are expensive and challenging to implement in decentralized storage scenarios. This paper proposes an efficient revocable multi-client BV-DSSE scheme with forward and Type III backward security. Firstly, we present a multi-client BV-DSSE relying on multiset hash functions and blockchain, achieving forward and Type III backward security while minimizing storage and computational overhead for users and on-chain operations. Secondly, we propose an efficient malicious user revocation protocol based on updatable encryption technology and introduce a two-tier access control mechanism to prevent unauthorized users from accessing private data. Finally, we implement and compare our proposed scheme with existing state-of-the-art solutions, indicating that our scheme has far lower storage and revocation overheads.