Cryptology ePrint Archive: Report 2017/367

Fork-Free Hybrid Consensus with Flexible Proof-of-Activity

Zhiqiang Liu and Shuyang Tang and Sherman S.M. Chow and Zhen Liu and Yu Long

Abstract: Bitcoin and its underlying blockchain mechanism have been attracting much attention. One of their core innovations, Proof-of-Work (PoW), is notoriously inefficient which potentially motivates a centralization of computing power, defeating the original goal of decentralization. Proof-of-Stake (PoS) is later proposed to replace PoW. However, both PoW and PoS have different inherent advantages and disadvantages, so does Proof-of-Activity (PoA) of Bentov et al. (SIGMETRICS 2014) which only offers limited combinations of two mechanisms. On the other hand, the hybrid consensus protocol of Pass and Shi (ePrint 16/917) aims to improve the efficiency by dynamically maintaining a rotating committee. Yet, there are unsatisfactory issues including chain forks and fair committee election. In this paper, we firstly devise a generalized variant of PoW. After that, we leverage our newly proposed generalized PoW to construct a fork-free hybrid consensus protocol, which addresses issues faced by the existing hybrid consensus mechanism. We further combine our fork-free hybrid consensus mechanism with PoS for a flexible version of PoA, which offers a flexible combination of PoW and PoS. Compared with Bentov et al.’s PoA, our “flexible PoA” improves the efficiency and provides more flexible combinations of PoW and PoS, resulting in a more powerful and applicable consensus protocol.

Category / Keywords: Blockchain, Consensus, Cryptocurrency, Hybrid Consen- sus, Practical Byzantine Fault Tolerance, Proof-of-Stake, Proof-of-Work.

Date: received 23 Apr 2017, last revised 13 Dec 2017

Contact author: htftsy at sjtu edu cn

Available format(s): PDF | BibTeX Citation

Version: 20171213:122154 (All versions of this report)

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