Tree-Based Sharding with Cross-Shard Virtual Payment Channels

Blockchain technology has experienced substantial development and has found extensive applications in the Internet of Things (IoT), which facilitates decentralized communications between devices. Blockchain enables individuals to record transactions, store data, and exchange value within a distributed ledger. However, with the development of blockchain, the performance bottleneck caused by scalability issues has become increasingly prominent. The sharding technique presents an effective solution to the scalability problem of blockchain systems by partitioning a complex blockchain network into multiple smaller node clusters. Each cluster independently maintains a ledger, reducing complexity and enhancing system efficiency. Besides, payment channels allow users to interact off-chain and rely on the security of the main chain for final settlement, accelerating the processing of numerous small transactions. However, existing sharding techniques face challenges with crossshard operations, including high conflict rates and inefficiencies in handling multiple small off-chain transactions. In this work, we propose a tree-based sharding protocol and by designing an ordering mechanism, our protocol could effectively resist front-running attacks. Furthermore, based on the proposed treebased sharding protocol, a cross-shard virtual channel protocol is designed and implemented for high-frequency cross-shard transactions. Finally, we implement a prototype for our protocol in Tendermint, which achieves 6700+ transaction throughput and lower confirmation latency both in intra-shard and cross-shard transactions with 16 shards compared to existing works, and we measure the cost of each phase of the cross-shard virtual channel protocol which takes approximately 250ms to process 300 transactions.