An Efficient and Robust Committee Structure for Sharding Blockchain

Nowadays, sharding is deemed a promising way to save traditional blockchain protocols from their low scalability. However, such a technique also brings several potential risks and a huge communication burden. An improper design may give rise to an inconsistent state among different committees. Further, the communication burden arising from cross-shard transactions, unfortunately, reduces the system's performance. In this paper, we first summarize five essential issues that all sharding blockchain designers face. For each issue, we discuss its key challenge and propose our suggested solutions. In order to break the performance bottlenecks, we design a committee structure and propose a reputation mechanism for selecting leaders. The term reputation in our design reflects each node's honest computation resources. In addition, we present a recovery procedure in case the leader is malicious. Theoretically, we prove that the system is robust under our design. Further simulation results also support this. In addition, the results show that selecting leaders by reputation can dramatically improve the system's performance.