On the complexity of fault-tolerant consensus

Dariusz R. Kowalski, Jarosław Mirek

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations


We consider the problem of reaching agreement in a distributed message-passing system prone to crash failures. Crashes are generated by Constrained adversaries - a Weakly-Adaptive adversary, who has to fix, in advance, the set of f crash-prone processes, and a k-Chain-Ordered adversary, who orders all the processes into k disjoint chains and has to follow this order when crashing them. Apart from these constraints, both of them may crash processes in an adaptive way at any time. While commonly used Strongly-Adaptive adversaries model attacks and Non-Adaptive ones - pre-defined faults, Constrained adversaries model more realistic scenarios when there are fault-prone dependent processes, e.g., in hierarchical or dependable software/hardware systems. In this view, our approach helps to understand better the crash-tolerant consensus in more realistic executions. We propose time-efficient consensus algorithms against such adversaries. We complement our algorithmic results with (almost) tight lower bounds, and extend the one for Weakly-Adaptive adversaries to hold also for (syntactically) weaker Non-Adaptive adversaries. Together with the consensus algorithm against Weakly-Adaptive adversaries (which automatically translates to the Non-Adaptive adversaries), these results extend the state-of-the-art of the popular class of Non-Adaptive adversaries, in particular, the result of Chor, Meritt and Shmoys [7], and prove separation gap between Constrained adversaries (including Non-Adaptive ones) and Strongly-Adaptive adversaries, analyzed by Bar-Joseph and Ben-Or [3] and others.

Original languageEnglish (US)
Title of host publicationNetworked Systems - 7th International Conference, NETYS 2019, Revised Selected Papers
EditorsMohamed Faouzi Atig, Alexander A. Schwarzmann
Number of pages13
ISBN (Print)9783030312763
StatePublished - 2019
Event7th International Conference on Networked Systems, NETYS 2019 - Marrakech, Morocco
Duration: Jun 19 2019Jun 21 2019

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume11704 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference7th International Conference on Networked Systems, NETYS 2019

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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