VKMRS: Efficient and Fair Blockchain-based Verifiable KGI-index-based Multi-keyword Ranked Search over Encrypted Cloud Server

This paper proposes VKMRS, a verifiable multi-keyword ranked search scheme that supports fair and privacy-preserving ranked searches on the blockchain, even with dynamic parameters, on large and complex datasets. The proposed scheme leverages a keyword-grouping-based inverted index (KGI-index) to protect the privacy of encrypted data and search/access patterns from adversaries, even under the known background model. Our work also utilizes smart contracts on the Ethereum blockchain to ensure fair payment and randomly verifies the search results for correctness and completeness. Theoretical analysis and experimental results demonstrate that the proposed model is efficient, secure, and offers feasible scenarios for complex and dynamic environments. Our work is valuable for large real-world applications demanding data integrity and confidentiality, such as financial services and healthcare, providing robust security, fair payment, and practical efficiency.