Brief Announcement: Polygraph: Accountable Byzantine Agreement

Authors Pierre Civit, Seth Gilbert, Vincent Gramoli

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Author Details

Pierre Civit
  • UPMC, Paris 6, France
Seth Gilbert
  • National University of Singapore, Singapore
Vincent Gramoli
  • The University of Sydney, Australia
  • EPFL, Lausanne, Switzerland

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Pierre Civit, Seth Gilbert, and Vincent Gramoli. Brief Announcement: Polygraph: Accountable Byzantine Agreement. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 45:1-45:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


In this paper, we introduce Polygraph, the first accountable Byzantine consensus algorithm. If among n users f < n/3 are malicious then it ensures consensus, otherwise it eventually detects malicious users that cause disagreement. Polygraph is appealing for blockchains as it allows to totally order blocks in a chain whenever possible, hence avoiding double spending and, otherwise, to punish at least n/3 malicious users when a fork occurs. This problem is more difficult than it first appears. Blockchains typically run in open networks whose delays are hard to predict, hence one cannot build upon synchronous techniques [Andreas Haeberlen et al., 2007; Vitalik Buterin and Virgil Griffith, 2019]. One may exploit cryptographic evidence of PBFT-like consensus [Miguel Castro and Barbara Liskov, 2002], however detecting equivocation would be insufficient. We show that it is impossible without extra logs of at least Ω(n) rounds [Pierre Civit et al., 2019]. Each round of Polygraph exchanges O(n²) messages.

Subject Classification

ACM Subject Classification
  • Security and privacy → Distributed systems security
  • Fault detection
  • cryptography
  • equivocation
  • consensus


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  1. Vitalik Buterin and Virgil Griffith. Casper the friendly finality gadget. Technical Report 1710.09437v4, arXiv, January 2019. URL:
  2. Miguel Castro and Barbara Liskov. Practical Byzantine fault tolerance and proactive recovery. ACM Transactions on Computer Systems, 20(4), 2002. Google Scholar
  3. Pierre Civit, Seth Gilbert, and Vincent Gramoli. Polygraph: Accountable Byzantine consensus. In Workshop on Verification of Distributed Systems (VDS), June 2019. Available at URL:
  4. Tyler Crain, Vincent Gramoli, Mikel Larrea, and Michel Raynal. DBFT: Efficient leaderless Byzantine consensus and its applications to blockchains. In IEEE NCA, 2018. URL:
  5. Andreas Haeberlen, Petr Kouznetsov, and Peter Druschel. PeerReview: Practical accountability for distributed systems. SOSP, 2007. Google Scholar