Opera: Reasoning about continuous common knowledge in asynchronous distributed systems

Sang Min Choi, Jiho Park, Quan Nguyen, Andre Cronje, Kiyoung Jang, Hyunjoon Cheon, Yo Sub Han, Byung Ik Ahn

Research output: Contribution to journalArticlepeer-review


This paper introduces a new family of consensus protocols, namely Lachesis-class denoted by L, for distributed networks with guaranteed Byzantine fault tolerance. Each Lachesis protocol L in L has complete asynchrony, is leaderless, has no round robin, no proof-of-work, and has eventual consensus. The core concept of our technology is the OPERA chain, generated by the Lachesis protocol. In the most general form, each node in Lachesis has a set of k neighbours of most preference. When receiving transactions a node creates and shares an event block with all neighbours. Each event block is signed by the hashes of the creating node and its k peers. The OPERA chain of the event blocks is a Directed Acyclic Graph (DAG); it guarantees practical Byzantine fault tolerance (pBFT). Our framework is then presented using Lamport timestamps and concurrent common knowledge. Further, we present an example of Lachesis consensus protocol L0 of our framework. Our L0 protocol can reach consensus upon 2/3 of all participants' agreement to an event block without any additional communication overhead. L0 protocol relies on a cost function to identify k peers and to generate the DAG-based OPERA chain. By creating a binary flag table that stores connection information and share information between blocks, Lachesis achieves consensus in fewer steps than pBFT protocol for consensus.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - 2018 Oct 4

All Science Journal Classification (ASJC) codes

  • General

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