Detecting and Punishing Mute Nodes in Shard-Based Permissionless Blockchains

As a key technology to solve the problem of trust in application systems, blockchain has attracted more and more attention in recent years. Many researches focus on applying voting-based consensus in permissionless blockchain to improve the throughput. However, in these methods, mute nodes may get the reward without participating in consensus, which may impact the availability of the system. We propose an observation exchanging protocol based on double-chain architecture to detect mute nodes. Nodes will vote on whether other nodes have sent protocol messages, and agree on an observation matrix which is generated by merging the observation of all nodes through consensus. We also propose an incentive mechanism and adopt a reputation system based on the matrix to punish mute nodes. Block reward is divided into three parts and is distributed according to the observation matrix. Security analysis shows that the observation exchanging protocol ensures mute nodes can be detected, and the incentive mechanism ensures mute nodes and the nodes adopt selfish strategies can be punished. Finally, we implement a prototype to evaluate our observation exchanging protocol and incentive mechanism. Experiment shows that the observation exchanging protocol merely has small influence on consensus delay.