An Adversarial Approach to Mitigating Lazy Voting Threats to Committee-Based Consensus

We identify a threat to blockchain networks utilizing committee-based consensus mechanisms, which we call “Lazy Agreement,” and provide a countermeasure through a reputation-based consensus mechanism we call “Adversarial Consensus.” Lazy Agreement occurs when a node within the committee is able skip validation of data and vote to agree by default assuming based on the assumptions that the committee is most likely honest. When the committee consists of mostly honest nodes, the data presented by other nodes will likely be honest and thus most committee nodes will vote to accept the data. While no problem occurs when honest data is proposed, the risk of malicious data being accepted is increased due to voting to accept without verification. Our research shows that even when a small percentage of nodes are malicious, the presence of lazy nodes resulted in malicious blocks being produced. We present a countermeasure wherein honest nodes periodically submit bad data to identify and punish lazy nodes using a reputation-based system for committee member selection. After implementation of the Adversarial Consensus mechanism within our simulated system, malicious block production was eliminated when the rate of adversarial block production was above 30% and at least 50% of the network was honest. At higher adversarial production rates, malicious block production was eliminated even when only 40% of the network nodes were honest. The penalization of lazy and malicious nodes further increases the probability that honest nodes will be selected for participation in consensus committees the longer the network is running.