MSig-BFT: A Witness-Based Consensus Algorithm for Private Blockchains

In this paper, we focus on the design of consensus algorithms for permission-based blockchains, i.e., private blockchains. In most consensus algorithms, blocks are proposed by a specific role called “leader”. In this paper, we introduce a new role called “witness” to supervise the leader. The presence of the witness facilitates the design of the consensus algorithm. We propose a witness-based consensus algorithm that guarantees safety and liveness. We implemented this consensus algorithm on Go Ethereum. The experimental result shows that in a blockchain where four nodes participate in the consensus process, we can achieve a throughput of 1000 transactions per second (TPS). Even if these four nodes are located on different continents, and one of them is faulty, we can still achieve a throughput of 300 TPS. Finally, we find that during the experiment, a significant portion of time is spent on activities other than the consensus task. The result suggests that to further increase the throughput of a private blockchain, the consensus task and non-consensus activities should be considered jointly.