ZLB，一种可容忍合谋多数节点的区块链
ZLB, a Blockchain Tolerating Colluding Majorities
AI总结：
本文提出拜占庭-欺诈-良性故障模型下共识可解性的新紧下界，基于Basilic类协议构建首个可容忍超半数合谋节点的ZLB区块链，实验证明其性能优于HotStuff，接近无法容忍n/3故障的Red Belly Blockchain。
摘要：
拜占庭共识问题一直是设计安全分布式系统的核心问题。但该问题的求解难度极大，主要原因在于存在可任意行事的拜占庭进程，且通用网络中的消息延迟具有不确定性。尽管学界早已明确，一旦出现n/3个拜占庭进程故障，共识的安全性与活性都会面临风险，但极少有研究尝试精确区分会导致安全性违规的故障与会导致终止性违规的故障。本文提出了共识问题可解性的一个新下界，我们将更通用的拜占庭故障细分为破坏安全性的欺诈性故障和破坏终止性的良性故障，该模型被称为拜占庭-欺诈-良性故障模型。我们证明，当$n \leq 3t + d + 2q$（其中t、d、q分别为拜占庭进程数、欺诈进程数和良性进程数）时，无法求解共识问题。我们还提出了Basilic类共识协议，证明该下界是紧的——当$n > 3t + d + 2q$时，这类协议可求解共识，不同协议的区别在于推进流程前等待接收消息的进程数量不同。随后，我们基于Basilic类协议提出了Zero-Loss Blockchain（ZLB），这是首个可容忍控制超过半数系统节点的对手的区块链，其中拜占庭节点占比最高不到三分之一。ZLB是一条开放区块链，结合了可问责拜占庭协议的最新理论进展，能够排除证据确凿的故障进程。值得注意的是，ZLB不需要已知的消息延迟上界，而是逐步将故障进程的比例降至1/3以下，最终达成共识。地理分布式实验表明，ZLB的性能优于HotStuff，速度几乎与可扩展的Red Belly Blockchain相当，而后者无法容忍n/3个故障。
英文摘要：
The problem of Byzantine consensus has been key to designing secure distributed systems. However, it is particularly difficult, mainly due to the presence of Byzantine processes that act arbitrarily and the unknown message delays in general networks. Although it is well known that both safety and liveness are at risk as soon as n/3 Byzantine processes fail, very few works attempted to characterize precisely the faults that produce safety violations from the faults that produce termination violations. In this paper, we present a new lower bound on the solvability of the consensus problem by distinguishing deceitful faults violating safety and benign faults violating termination from the more general Byzantine faults, in what we call the Byzantine-deceitful-benign fault model. We show that one cannot solve consensus if $n \leq 3t + d + 2q$ with t, d, and q are Byzantine, deceitful, and benign processes. We show that this bound is tight by presenting the Basilic class of consensus protocols that solve consensus when $n > 3t + d + 2q$. These protocols differ in the number of processes from which they wait to receive messages before progressing. Then, we build upon the Basilic class in order to present Zero-Loss Blockchain (ZLB), the first blockchain that tolerates an adversary controlling more than half of the system, with up to less than a third of them Byzantine. ZLB is an open blockchain that combines recent theoretical advances in accountable Byzantine agreement to exclude undeniably faulty processes. Interestingly, ZLB does not need a known bound on the delay of messages but progressively reduces the portion of faulty processes below 13 , and reaches consensus. Geo-distributed experiments show that ZLB outperforms HotStuff and is almost as fast as the scalable Red Belly Blockchain that cannot tolerate n/3 faults.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
