Brief Announcement: Ordered Reliable Broadcast and Fast Ordered Byzantine Consensus for Cryptocurrency

Abstract

The problem of transaction reordering in blockchains, also known as the blockchain anomaly [11], can lead to fairness limitations [8] and front-running activities [6] in cryptocurrency. To cope with this problem despite f < n3 byzantine processes, Zhang et al. [12] have introduced the ordering linearizability property ensuring that if two transactions or commands are perceived by all correct processes in the same order, then they are executed in this order. They proposed a generic distributed protocol that first orders commands and then runs a leader-based consensus protocol to agree on these orders, hence requiring at least 11 message delays. In this paper, we parallelize the ordering with the execution of the consensus to require only 6 message delays. For the ordering, we introduce the ordered reliable broadcast primitive suitable for broadcast-based cryptocurrencies (e.g., [3]). For the agreement, we build upon the DBFT leaderless consensus protocol [4] that was recently formally verified [1]. The combination is thus suitable to ensure ordering linearizability in consensus-based cryptocurrencies (e.g., [5]). 2012 ACM Subject Classification Computing methodologies → Distributed algorithms