Visible to the public Modeling the Impact of Network Connectivity on Consensus Security of Proof-of-Work Blockchain

TitleModeling the Impact of Network Connectivity on Consensus Security of Proof-of-Work Blockchain
Publication TypeConference Paper
Year of Publication2020
AuthorsXiao, Y., Zhang, N., Lou, W., Hou, Y. T.
Conference NameIEEE INFOCOM 2020 - IEEE Conference on Computer Communications
Date PublishedJuly 2020
ISBN Number978-1-7281-6412-0
Keywordsanalytical model, Analytical models, bitcoin, blockchain, blockchain forks, blockchain system, central trusted authority, consensus protocol, consensus security, consensus voting power, cryptographic protocols, cryptography, data mining, design system, different adversary models, distributed consensus system, electronic money, financial data processing, honest-but-potentially-colluding, honest-majority, Human Behavior, modeling analysis, network connectivity, Network modeling, node behavior, Peer-to-peer computing, PoW blockchain, Probabilistic logic, proof-of-work blockchain, Protocols, pubcrawl, Scalability, security, security impact, security of data, security properties, telecommunication security

Blockchain, the technology behind the popular Bitcoin, is considered a "security by design" system as it is meant to create security among a group of distrustful parties yet without a central trusted authority. The security of blockchain relies on the premise of honest-majority, namely, the blockchain system is assumed to be secure as long as the majority of consensus voting power is honest. And in the case of proof-of-work (PoW) blockchain, adversaries cannot control more than 50% of the network's gross computing power. However, this 50% threshold is based on the analysis of computing power only, with implicit and idealistic assumptions on the network and node behavior. Recent researches have alluded that factors such as network connectivity, presence of blockchain forks, and mining strategy could undermine the consensus security assured by the honest-majority, but neither concrete analysis nor quantitative evaluation is provided. In this paper we fill the gap by proposing an analytical model to assess the impact of network connectivity on the consensus security of PoW blockchain under different adversary models. We apply our analytical model to two adversarial scenarios: 1) honest-but-potentially-colluding, 2) selfish mining. For each scenario, we quantify the communication capability of nodes involved in a fork race and estimate the adversary's mining revenue and its impact on security properties of the consensus protocol. Simulation results validated our analysis. Our modeling and analysis provide a paradigm for assessing the security impact of various factors in a distributed consensus system.

Citation Keyxiao_modeling_2020