Consensus in equilibrium: Can one against all decide fairly?

Itay Harel, Amit Jacob-Fanani, Moshe Sulamy, Yehuda Afek

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

Abstract

Is there an equilibrium for distributed consensus when all agents except one collude to steer the decision value towards their preference? If an equilibrium exists, then an n − 1 size coalition cannot do better by deviating from the algorithm, even if it prefers a different decision value. We show that an equilibrium exists under this condition only if the number of agents in the network is odd and the decision is binary (among two possible input values). That is, in this framework we provide a separation between binary and multi-valued consensus. Moreover, the input and output distribution must be uniform, regardless of the communication model (synchronous or asynchronous). Furthermore, we define a new problem - Resilient Input Sharing (RIS), and use it to find an iff condition for the (n − 1)-resilient equilibrium for deterministic binary consensus, essentially showing that an equilibrium for deterministic consensus is equivalent to each agent learning all the other inputs in some strong sense. Finally, we note that (n − 2)-resilient equilibrium for binary consensus is possible for any n. The case of (n − 2)-resilient equilibrium for multi-valued consensus is left open.

Original languageEnglish
Title of host publication23rd International Conference on Principles of Distributed Systems, OPODIS 2019
EditorsPascal Felber, Roy Friedman, Seth Gilbert, Avery Miller
PublisherSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
ISBN (Electronic)9783959771337
DOIs
StatePublished - Feb 2020
Event23rd International Conference on Principles of Distributed Systems, OPODIS 2019 - Neuchatel, Switzerland
Duration: 17 Dec 201919 Dec 2019

Publication series

NameLeibniz International Proceedings in Informatics, LIPIcs
Volume153
ISSN (Print)1868-8969

Conference

Conference23rd International Conference on Principles of Distributed Systems, OPODIS 2019
Country/TerritorySwitzerland
CityNeuchatel
Period17/12/1919/12/19

Keywords

  • Consensus
  • Distributed computing
  • Game theory
  • Rational agents

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