veffChain: Enabling Freshness Authentication of Rich Queries Over Blockchain Databases

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
$\mathsf{veffChain}$
and
$\mathsf{veffChain++}$
, to realize freshness authentication of rich queries over blockchain databases. Specifically,
$\mathsf{veffChain}$
concerns about verifiable latest-
$K$
exact queries and employs RSA accumulator to generate constant-size ADSs;
$\mathsf{veffChain++}$
integrates RSA accumulator into the Trie tree to further authenticate latest-
$K$
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.