具有因果排序的拜占庭可靠广播
Byzantine Reliable Broadcast with Causal Ordering
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中文总结 AI 辅助
针对拜占庭故障下可靠广播缺乏因果排序的问题，提出基于联合观察的完整定义及高效协议，容忍最优故障数，实现因果排序。
中文摘要 AI 辅助
在拜占庭故障模型下，可靠广播和全序广播已被广泛研究，但添加因果顺序却受到的关注相对较少，这主要是因为拜占庭进程的行为所带来的复杂性。现有解决方案几乎都在全序广播之上构建因果排序。将因果顺序与可靠广播相结合仍然很少见，而现有的少数解决方案采用了基于单个进程上发生的事件（即“发生于之前”关系）的经典因果性定义。这一定义不足以在广播消息之间强制执行因果排序：拜占庭进程可以谎报、省略和伪造依赖信息，从而违反自报事件之间的因果顺序。此类操纵对于任何单个观察者而言，与正确行为无法区分。我们通过一次抢先交易攻击来展示该问题及其后果。为了弥补这一差距，我们将可靠广播的概念扩展，以外部化本地潜在知识。我们利用这一点，在拜占庭故障下，首次形式化了可靠广播中因果消息排序的完整定义。与经典形式化不同，这一概念基于足够大的正确进程组的联合观察，而非单个进程自身的视角。基于这一定义，我们刻画了保证因果排序的拜占庭可靠广播信道的性质。随后，我们提出了一种满足这些性质的高效协议：它能容忍最优数量的 $f < n/3$ 个拜占庭故障，并且对于广播负载消息~$m$ 的一个实例，其比特复杂度为 $O(n^2(|m| + \lambda + n))$，其中 $\lambda$ 表示 $m$ 的唯一（密码学）标签的最大大小。最后，我们证明了该协议实现了具有因果排序的拜占庭可靠广播。
英文摘要
Reliable and total-order broadcasts in the Byzantine-fault model are well studied, but adding causal order has received comparatively little attention, largely due to the complexity that stems from actions of Byzantine processes. Existing solutions almost exclusively build causal ordering on top of total-order broadcast. The combination of causal order with reliable broadcast remains rare, and the few solutions that exist adopt the classical definition of causality based on events occurring at individual processes (the happened-before relation). This definition is not sufficient to enforce causal ordering among broadcast messages: Byzantine processes can lie about, omit, and forge dependency information and thereby violate the causal order among self-reported events. Such manipulations remain indistinguishable from correct behavior to any single observer. We demonstrate the issue and its consequences via a front-running attack. To close this gap, we extend the notion of reliable broadcast to externalize local potential knowledge. We use this to formalize the first complete definition of causal message ordering in reliable broadcast under Byzantine faults. Unlike the classical formalization, this notion is grounded in the joint observations of a sufficiently large group of correct processes rather than a process's own view. Building on this definition, we characterize the properties of a Byzantine reliable broadcast channel that guarantees causal ordering. We then present an efficient protocol that satisfies these properties: it is resilient to the optimal number of $f < n/3$ Byzantine faults and for one instance that broadcasts payload message~$m$, it has bit complexity $O(n^2(|m| + λ+ n))$, where $λ$ denotes the maximal size of a unique (cryptographic) label for~$m$. Finally, we prove the protocol achieves Byzantine reliable broadcast with causal ordering.
发表机构
- University of Bern（伯尔尼大学）
机构由 AI 辅助整理，请以论文原文为准。
