Fork Accountability in Tenderbake

Authors Antonella Del Pozzo, Thibault Rieutord

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Antonella Del Pozzo
  • Université Paris-Saclay, CEA, List, F-91120, Palaiseau, France
Thibault Rieutord
  • Université Paris-Saclay, CEA, List, F-91120, Palaiseau, France


The authors warmly thank Lăcrămioara Aştefănoaei, Eugen Zălinescu and Sara Tucci-Pieriogvanni for all the insightful discussions that improved the quality of this work.

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Antonella Del Pozzo and Thibault Rieutord. Fork Accountability in Tenderbake. In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 5:1-5:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


This work investigates the Fork Accountability problem in the BFT-Consensus-based Blockchain context. When there are more attackers than the tolerated ones, BFT-Consensus may fail in delivering safety. When this occurs, Fork Accountability aims to account for the responsible processes for that safety violation. As a case study, we consider Tenderbake when the assumption on the maximum number of Byzantine validators - participants involved in creating the next block - does not hold anymore. When a fork occurs, there are more than one-third of Byzantine validators, and we aim to account for the responsible validators to remove them from the system. In this work, we compare three different approaches to implementing accountability in the case of a fork. In particular, we show that in the case of a fork, if we do not modify Tenderbake or we enrich it with a reliable broadcast communication abstraction, then we can account Byzantine processes only in particular scenarios. Contrarily, if we change Tenderbake such that the exchanged messages also carry extra information (which size is proportional to the duration of the current consensus computation), then we can account for Byzantine processes in all kinds of scenarios; however, at the cost of unbounded message size and unbounded local memory.

Subject Classification

ACM Subject Classification
  • Theory of computation → Distributed algorithms
  • Blockchain
  • BFT-Consensus
  • Fork Accountability


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