Scaling proof-of-authority protocol to improve performance and security

Following the widespread application of blockchain, a variety of consensus protocols have been proposed recently for different scenarios. Proof of Authority (PoA) is a newly proposed Byzantine Fault Tolerant (BFT) consensus protocol for permissioned blockchains. It relies on a set of trusted nodes to generate blocks and adopts the longest-chain rule to reach consensus. However, the protocol suffers from performance and security issues due to its simple design. This paper proposes CoPoA, a novel proof-of-authority protocol that aims to improve performance and security. In terms of performance, we allow all authority nodes to generate blocks concurrently and process all types of blocks to improve throughput and feedback their blockchain information to the rest of the nodes on time to provide fast confirmation. In terms of security, we select the leader by a random number and set a tight confirmation boundary to protect the protocol from attack. We make a theoretical analysis to prove the safety and liveness properties of the protocol and demonstrate its performance through a prototype implementation and multiple tests. In our experiments, when the number of authority nodes is 9, CoPoA achieves 2x throughput improvement and 5x latency reduction compared to the original PoA protocol.