Selfish & opaque transaction ordering in the Bitcoin blockchain: The case for chain neutrality

Johnnatan Messias, Mohamed Alzayat, Balakrishnan Chandrasekaran, Krishna P. Gummadi, Patrick Loiseau, Alan Mislove

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

Abstract

Most public blockchain protocols, including the popular Bitcoin and Ethereum blockchains, do not formally specify the order in which miners should select transactions from the pool of pending (or uncommitted) transactions for inclusion in the blockchain. Over the years, informal conventions or "norms"for transaction ordering have, however, emerged via the use of shared software by miners, e.g., the GetBlockTemplate (GBT) mining protocol in Bitcoin Core. Today, a widely held view is that Bitcoin miners prioritize transactions based on their offered "transaction fee-per-byte."Bitcoin users are, consequently, encouraged to increase the fees to accelerate the commitment of their transactions, particularly during periods of congestion. In this paper, we audit the Bitcoin blockchain and present statistically significant evidence of mining pools deviating from the norms to accelerate the commitment of transactions for which they have (i) a selfish or vested interest, or (ii) received dark-fee payments via opaque (non-public) side-channels. As blockchains are increasingly being used as a record-keeping substrate for a variety of decentralized (financial technology) systems, our findings call for an urgent discussion on defining neutrality norms that miners must adhere to when ordering transactions in the chains. Finally, we make our data sets and scripts publicly available.

Original languageEnglish
Title of host publicationIMC 2021
Subtitle of host publicationProceedings of the 2021 ACM Internet Measurement Conference
PublisherAssociation for Computing Machinery
Pages320-335
Number of pages16
ISBN (Electronic)9781450391290
DOIs
Publication statusPublished - Nov 2021
Event21st ACM Internet Measurement Conference, IMC 2021 - Virtual, Online, United States
Duration: 2 Nov 20214 Nov 2021

Publication series

NameProceedings of the ACM SIGCOMM Internet Measurement Conference, IMC

Conference

Conference21st ACM Internet Measurement Conference, IMC 2021
Country/TerritoryUnited States
CityVirtual, Online
Period2/11/214/11/21

Bibliographical note

Funding Information:
K. P. Gummadi acknowledges support from the European Research Council (ERC) Advanced Grant “Foundations for Fair Social Computing,” funded under the European Union’s Horizon 2020 Frame-work Programme (grant agreement no. 789373). P. Loiseau was supported by MIAI @ Grenoble Alpes (ANR-19-P3IA-0003) and by the French National Research Agency through grant ANR-20-CE23-0007. A. Mislove acknowledges support from NSF grants CNS-1900879 and CNS-1955227.

Publisher Copyright:
© 2021 Owner/Author.

Funding

K. P. Gummadi acknowledges support from the European Research Council (ERC) Advanced Grant “Foundations for Fair Social Computing,” funded under the European Union’s Horizon 2020 Frame-work Programme (grant agreement no. 789373). P. Loiseau was supported by MIAI @ Grenoble Alpes (ANR-19-P3IA-0003) and by the French National Research Agency through grant ANR-20-CE23-0007. A. Mislove acknowledges support from NSF grants CNS-1900879 and CNS-1955227.

FundersFunder number
Horizon 2020 Frame-work Programme
MIAI @ Grenoble AlpesANR-19-P3IA-0003
National Science FoundationCNS-1955227, CNS-1900879
Horizon 2020 Framework Programme789373
European Research Council
Agence Nationale de la RechercheANR-20-CE23-0007

    Keywords

    • blockchain
    • transaction commit times
    • transaction ordering

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