Leader-based protocols for consensus, i.e., atomic broadcast, allow some processes to unilaterally affect the final order of transactions. This has become a problem for blockchain networks and decentralized finance because it facilitates front-running and other attacks. To address this, order fairness for payload messages has been introduced recently as a new safety property for atomic broadcast complementing traditional agreement and liveness. We relate order fairness to the standard validity notions for consensus protocols and highlight some limitations with the existing formalization. Based on this, we introduce a new differential order-fairness property that fixes these issues. We also present the quick order-fair atomic broadcast protocol that guarantees payload message delivery in a differentially fair order and is much more efficient than existing order-fair consensus protocols. It works for asynchronous and for eventually synchronous networks with optimal resilience, tolerating corruptions of up to one third of the processes. Previous solutions required there to be less than one fourth of faults. Furthermore, our protocol incurs only quadratic cost, in terms of amortized message complexity per delivered payload.
翻译:以领导人为基础的共识协议,即原子广播,允许某些程序单方面影响交易的最终顺序。这已成为链链网络和分散融资的一个问题,因为它有利于前期运行和其他袭击。为了解决这个问题,最近推出了有效载荷信息定级公平,作为原子广播的新安全属性,以补充传统协议和活性。我们把秩序公平与协商一致协议的标准有效性概念联系起来,并突出现有正式化的一些限制。在此基础上,我们引入了一种新的差异性秩序公平属性,以修补这些问题。我们还介绍了快速、公平、原子广播协议,保证有效载荷信息以不同公平顺序发送,比现有的秩序-公平共识协议效率高得多。它有助于无节制,最终实现同步网络和最佳复原力,容忍高达三分之一的进程的腐败。先前的解决办法需要少于四分之一的误差。此外,我们的协议仅产生按交付的有效有效载荷分解信息复杂性计算的二次成本。