부산대학교 도서관

With the wide adoption of blockchains in data-intensive applications, enabling verifiable queries over a blockchain database is urgently required. Aiming at reducing costs, previous solutions embed a small-sized authenticated data structure (ADS) in each block header, so that a user can verify search results without maintaining a full copy of blockchain databases. However, existing studies focus on exact queries with difficulty to guarantee the freshness of search results. In this article, we propose two frameworks, called $\mathsf{veffChain}$veffChain and $\mathsf{veffChain++}$veffChain++, to realize freshness authentication of rich queries over blockchain databases. Specifically, $\mathsf{veffChain}$veffChain concerns about verifiable latest-$K$K exact queries and employs RSA accumulator to generate constant-size ADSs; $\mathsf{veffChain++}$veffChain++ integrates RSA accumulator into the Trie tree to further authenticate latest-$K$K fuzzy queries. For improved scalability, an adaptive keyword splitting (AKS) solution is proposed to enable ADSs to be incrementally updated. Compared with the state-of-the-art work, our frameworks have the following merits: (1) Freshness Guarantee . The user can efficiently retrieve the freshest data from a blockchain database in a verifiable way. (2) Flexibility . The user can specify different query patterns on demand to retrieve data as accurately as possible. The detailed security analysis and extensive experiments validate the practicality of our frameworks.