Parallel Proof-of-Work (PoW) protocols have been suggested in the literature to improve the safety guarantees, transaction throughput and confirmation latencies of Nakamoto consensus. In this work, we first consider the existing parallel PoW protocols and develop hard-coded incentive attack structures. Our theoretical results and simulations show that the existing parallel PoW protocols are more vulnerable to incentive attacks than the Nakamoto consensus, e.g., attacks have smaller profitability threshold and they result in higher relative rewards. Next, we introduce a voting-based semi-parallel PoW protocol that outperforms both Nakamoto consensus and the existing parallel PoW protocols from most practical perspectives such as communication overheads, throughput, transaction conflicts, incentive compatibility of the protocol as well as a fair distribution of transaction fees among the voters and the leaders. We use state-of-the-art analysis to evaluate the consistency of the protocol and consider Markov decision process (MDP) models to substantiate our claims about the resilience of our protocol against incentive attacks.

翻译：并行工作量证明（PoW）协议在已有文献中被提出，旨在提升中本共识的安全性保障、交易吞吐量及确认延迟。本文首先考察现有并行PoW协议，并构建了硬编码的激励攻击结构。理论结果与仿真实验表明，现有并行PoW协议相比中本共识更易受激励攻击，例如攻击的盈利阈值更低且能获得更高的相对收益。随后，我们提出一种基于投票的半并行PoW协议，该协议在通信开销、吞吐量、交易冲突、协议激励相容性以及投票者与领导者间交易费用的公平分配等多数实践维度上，均优于中本共识与现有并行PoW协议。我们采用前沿分析方法评估协议的一致性，并利用马尔可夫决策过程（MDP）模型验证本协议抵御激励攻击的稳健性主张。