Consensus of Whom? A Spectrum of Blockchain Consensus Protocols and New Directions

Abstract

Blockchain technology aims to maintain a consistent ledger which is kept by the nodes of the system in a distributed manner. To achieve this goal, a consensus protocol needs to be employed for the nodes to process the block data and exchange their validation opinions. A variety of consensus protocols have been proposed for different application scenarios. In this paper, we propose a framework of categorizing consensus protocols based on the number, role and selection of nodes to be involved in the validation and ordering procedure. We also identify several possible new directions of consensus protocol design for future blockchain applications.