Supporting efficient and verifiable keyword queries on dynamic blockchain data

The hybrid-storage blockchain relieves on-chain storage constraints by storing raw data off-chain and retaining only data hashes on-chain. An authenticated data structure (ADS) ensures secure, verifiable queries within this architecture. A significant challenge arises when on-chain nodes must update the root digest after inserting new data objects into the ADS. Most existing research has focused only on static data scenarios. This paper introduces a novel keyword query framework for encrypted data, enabling the synchronized maintenance of the ADS on-chain. The proposed ADS assigns a unique keyword to each leaf node and fixes the ADS’s tree topology based on historical data. To accommodate new data, we develop specific keyword binding and update rules. To minimize root digest updates, we separate the digest construction of the search key from the data content. The data content digest is computed using the Mercury commitment. This approach ensures the root digest remains unchanged when a new data object is added. The fixed topology makes updating the ADS’s root digest simple. Keyword binding and update rules further reduce the frequency of root digest updates associated with keywords Extensive experimental evaluation results show the superiority of our proposed method in both query time and VO size. • Efficient verifiable keyword queries of encrypted data in hybrid-storage blockchain. • Lightweight on-chain digest maintenance without full authenticated data structure. • Minimizing on-chain digest updates when inserting new data objects. • Generating separate digests for the search key and the data content.