Efficient Verifiable Boolean Range Query for Light Clients on Blockchain Database

Abstract

Blockchain allows clients to query and verify any transactions, which requires the clients to maintain the entire blockchain database locally. This approach is inadvisable because the blockchain database is an append-only ledger and incurs significant maintenance overhead. Very recently, blockchain light client has attracted considerable concerns, which relies on a third party (i.e., a full node) to perform query processing and verification. However, the dishonest full node may return an incorrect and incomplete result of the query requests. Therefore, it remains a challenging issue to achieve secure, efficient, and rich verifiable queries for light clients. In this paper, we propose an efficient verifiable Boolean range query scheme for light clients on the blockchain database. Firstly, we design a new authenticated data structure, polynomial commitment B + -tree (PCB-tree), which efficiently ensures the correctness and completeness of Boolean range queries for blockchain light clients. Secondly, we provide a tunable trade-off between query time and communication overhead by autonomously setting the fanout size of the PCB-tree. Moreover, our scheme can support batch processing to reduce query complexity and proof size. Finally, security analysis and performance evaluation show that our proposed scheme is secure and practical.