Agreement protocols are crucial in various emerging applications, spanning from distributed (blockchains) oracles to fault-tolerant cyber-physical systems. In scenarios where sensor/oracle nodes measure a common source, maintaining output within the convex range of correct inputs, known as convex validity, is imperative. Present asynchronous convex agreement protocols employ either randomization, incurring substantial computation overhead, or approximate agreement techniques, leading to high $\mathcal{\tilde{O}}(n^3)$ communication for an $n$-node system. This paper introduces Delphi, a deterministic protocol with $\mathcal{\tilde{O}}(n^2)$ communication and minimal computation overhead. Delphi assumes that honest inputs are bounded, except with negligible probability, and integrates agreement primitives from literature with a novel weighted averaging technique. Experimental results highlight Delphi's superior performance, showcasing a significantly lower latency compared to state-of-the-art protocols. Specifically, for an $n=160$-node system, Delphi achieves an 8x and 3x improvement in latency within CPS and AWS environments, respectively.

翻译：一致协议在从分布式（区块链）预言机到容错信息物理系统的各类新兴应用中至关重要。当传感器/预言机节点测量同一信号源时，必须将输出维持在正确输入值的凸包范围内——即满足凸有效性。现有的异步凸一致协议要么采用随机化方法（导致大量计算开销），要么采用近似一致技术（导致 $n$ 节点系统产生高达 $\mathcal{\tilde{O}}(n^3)$ 的通信复杂度）。本文提出德菲协议（Delphi），这是一种确定性协议，其通信复杂度仅为 $\mathcal{\tilde{O}}(n^2)$，且计算开销极低。该协议假设诚实节点的输入以可忽略的概率有界，并将文献中的一致原语与新型加权平均技术相结合。实验结果表明，德菲协议具有显著优势，相较于现有最优协议实现了更低的延迟。具体而言，在 $n=160$ 节点的系统中，德菲协议在信息物理系统与亚马逊云服务环境中的延迟分别提升了 8 倍和 3 倍。