SDB: Scalable Blockchain Database via Searchable Encryption and Cross-Shard Mechanism

Blockchain database has been widely applied in various fields, providing a secure architecture for data storage and sharing. In blockchain databases, the use of sharding technology can enhance the system's scalability and improve the processing capabilities for data and transactions. However, when applying searchable encryption techniques to query encrypted data in sharding blockchains, frequent data access to different shards can result in uneven load distribution, leading to hotspot issues and reducing system efficiency. To tackle the challenge, we present$S D B$, a scheme integrating searchable encryption with sharding technology to enhance the scalability of blockchain databases. We present a cross-shard query strategy based on encrypted indexes, which constructs verifiable indexes for encrypted data. This addresses the cross-shard query optimization problem in encrypted environments. Under the experiment and security analysis,$S D B$achieves efficient cross-shard queries with higher query performance and throughput, at least 30% higher than state-of-the-art scalable blockchain database schemes.