Oracle networks feeding off-chain information to a blockchain are required to solve a distributed agreement problem since these networks receive information from multiple sources and at different times. We make a key observation that in most cases, the value obtained by oracle network nodes from multiple information sources are in close proximity. We define a notion of agreement distance and leverage the availability of a state machine replication (SMR) service to solve this distributed agreement problem with an honest simple majority of nodes instead of the conventional requirement of an honest super majority of nodes. Values from multiple nodes being in close proximity, therefore, forming a coherent cluster, is one of the keys to its efficiency. Our asynchronous protocol also embeds a fallback mechanism if the coherent cluster formation fails. Through simulations using real-world exchange data from seven prominent exchanges, we show that even for very small agreement distance values, the protocol would be able to form coherent clusters and therefore, can safely tolerate up to $1/2$ fraction of Byzantine nodes. We also show that, for a small statistical error, it is possible to choose the size of the oracle network to be significantly smaller than the entire system tolerating up to a $1/3$ fraction of Byzantine failures. This allows the oracle network to operate much more efficiently and horizontally scale much better.

翻译：预言机网络需将从链下获取的信息输送至区块链，由于这些网络从多个源且在不同时间接收信息，因此必须解决分布式共识问题。我们观察到关键现象：在多数情况下，预言机网络节点从多个信息源获取的值彼此接近。据此定义“共识距离”概念，并借助状态机复制服务，使用诚实简单多数节点（而非传统要求的诚实超多数节点）解决此分布式共识问题。多节点值彼此接近形成一致性簇，是实现高效性的关键之一。我们的异步协议还嵌入了当一致性簇形成失败时的回退机制。通过使用七家主流交易所的真实市场数据仿真，结果表明即使采用极小的共识距离值，该协议仍能形成一致性簇，因此可安全容忍高达1/2比例的拜占庭节点。我们同时证明，在微小统计误差下，可将预言机网络规模选择为显著小于整个系统，且能容忍高达1/3比例的拜占庭故障。这使得预言机网络运行效率显著提升，横向扩展能力大为增强。