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：将链下信息馈送至区块链的预言机网络需要解决分布式共识问题，因为这些网络从多个来源及不同时间接收信息。我们观察到，在大多数情况下，预言机网络节点从多个信息源获取的值彼此非常接近。我们定义了“共识距离”概念，并利用状态机复制服务的可用性，以诚实简单多数节点替代传统要求的诚实超多数节点来解决该分布式共识问题。多个节点的值彼此接近从而形成连贯集群，是实现高效性的关键之一。我们的异步协议还内置了当连贯集群形成失败时的回退机制。通过使用来自七个主要交易所的真实世界交易数据进行模拟，我们证明即使采用极小的共识距离值，该协议仍能形成连贯集群，从而安全容忍高达1/2比例的拜占庭节点。我们还表明，在较小的统计误差下，可将预言机网络规模选择为显著小于整个系统，同时容忍高达1/3比例的拜占庭故障。这使得预言机网络能够以更高效率运行，并实现更好的水平扩展性。