Komorebi: A DAG-based Asynchronous BFT Consensus via Sharding
Song Peng, Yang Liu, Jingwen Chen, Jinlong He, Yaoqi Wang · 2023
The consensus mechanism, as a core technology of blockchain, plays a crucial role in ensuring system consistency and reliability. Existing consensus algorithms adopt a Directed Acyclic Graph (DAG) structure to improve the throughput of blockchain systems. However, when unstable network connections or network partitions occur, a large number of blocks may be lost, and work may be wasted, resulting in a significant drop in system performance. We propose an asynchronous Byzantine fault-tolerant consensus protocol, Komorebi, based on DAG and sharding. The protocol divides the blockchain network into multiple shards, allowing for parallel processing of different transaction sets to enhance the scalability and network partition tolerance of the blockchain, thus avoiding the bottleneck problem of a single chain in the blockchain. Komorebi utilizes structured DAG inside each shard to achieve parallel broadcasting and transaction processing. Nodes only broadcast and store transaction blocks of their local shards, which improves transaction processing efficiency and reduces storage overhead. For inter-shard communication, nodes transmit block events instead of blocks, significantly reducing communication overhead between shards. Furthermore, through inter-shard communication, nodes in different shards can maintain a consistent global block event status, solving security degradation issues caused by sharding. Experimental results show that Komorebi achieves a throughput of over 190,000 tx/s with a delay of less than 2 seconds in a 64-node network with 16 shards.