Fact and fiction: challenging the honest majority assumption of permissionless blockchains

Runchao Han, Zhimei Sui, Jiangshan Yu, Joseph Liu, Shiping Chen

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

4 Citations (Scopus)

Abstract

Honest majority is the key security assumption of Proof-of-Work (PoW) based blockchains. However, the recent 51% attacks render this assumption unrealistic in practice. In this paper, we challenge this assumption against rational miners in the PoW-based blockchains in reality. In particular, we show that the current incentive mechanism may encourage rational miners to launch 51% attacks in two cases. In the first case, we consider a miner of a stronger blockchain launches 51% attacks on a weaker blockchain, where the two blockchains share the same mining algorithm. In the second case, we consider a miner rents mining power from cloud mining services to launch 51% attacks. As 51% attacks lead to double-spending, the miner can profit from these two attacks. If such double-spending is more profitable than mining, miners are more intended to launch 51% attacks rather than mine honestly. We formally model such behaviours as a series of actions through a Markov Decision Process. Our results show that, for most mainstream PoW-based blockchains, 51% attacks are feasible and profitable, so profit-driven miners are incentivised to launch 51% attacks to gain extra profit. In addition, we leverage our model to investigate the recent 51% attack on Ethereum Classic (on 07/01/2019), which is suspected to be an incident of 51% attacks. We provide insights on the attacker strategy and expected revenue, and show that the attacker's strategy is near-optimal.

Original languageEnglish
Title of host publicationASIA CCS'21 - Proceedings of the 2021 ACM Asia Conference on Computer and Communications Security
EditorsTsz Hon Yuen
Place of PublicationNew York NY USA
PublisherAssociation for Computing Machinery (ACM)
Pages817-831
Number of pages15
ISBN (Electronic)9781450382878
DOIs
Publication statusPublished - 2021
EventACM Asia Conference on Computer and Communications Security 2021 - Online, Hong Kong
Duration: 7 Jun 202111 Jun 2021
Conference number: 16th
https://dl.acm.org/doi/proceedings/10.1145/3433210 (Proceedings)

Conference

ConferenceACM Asia Conference on Computer and Communications Security 2021
Abbreviated titleAsiaCCS 2021
Country/TerritoryHong Kong
Period7/06/2111/06/21
Internet address

Keywords

  • 51% attacks
  • blockchain
  • proof-of-work

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