An Efficient and Robust Committee Structure for Sharding Blockchain
This work addresses scalability and security issues for blockchain systems, but it is incremental as it builds on existing sharding techniques with specific enhancements.
The paper tackles the problem of inconsistent states and high communication overheads in sharding blockchains by proposing a reputation-based leader selection mechanism and a recovery procedure with a referee committee, resulting in dramatically improved system performance as shown in simulations.
Nowadays, sharding is deemed as a promising way to save traditional blockchain protocols from their low scalability. However, such technique also brings several potential risks and huge communication overheads. An improper design may give rise to the inconsistent state among different committees. Further, the communication overheads arising from cross-shard transactions unfortunately reduce 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 propose a reputation mechanism for selecting leaders. The term of reputation in our design reflects each node's honest computation resources. In addition, we introduce a referee committee and partial sets in each committee, and design a recovery procedure in case the leader is malicious. Under the design, we prove that malicious leaders will not hurt the system and will be evicted. Furthermore, we conduct a series of simulations to evaluate our design. The results show that selecting leaders by the reputation can dramatically improve the system performance.