Faithful Simulation of Randomized BFT Protocols on Block DAGs

Authors Hagit Attiya , Constantin Enea , Shafik Nassar

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Author Details

Hagit Attiya
  • Technion, Haifa, Israel
Constantin Enea
  • LIX, Ecole Polytechnique, CNRS and Institut Polytechnique de Paris, France
Shafik Nassar
  • Technion, Haifa, Israel

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Hagit Attiya, Constantin Enea, and Shafik Nassar. Faithful Simulation of Randomized BFT Protocols on Block DAGs. In 34th International Conference on Concurrency Theory (CONCUR 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 279, pp. 27:1-27:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


Byzantine Fault-Tolerant (BFT) protocols that are based on Directed Acyclic Graphs (DAGs) are attractive due to their many advantages in asynchronous blockchain systems. These DAG-based protocols can be viewed as a simulation of some BFT protocol on a DAG. Many DAG-based BFT protocols rely on randomization, since they are used for agreement and ordering of transactions, which cannot be achieved deterministically in asynchronous systems. Randomization is achieved either through local sources of randomness, or by employing shared objects that provide a common source of randomness, e.g., common coins. A DAG simulation of a randomized protocol should be faithful, in the sense that it precisely preserves the properties of the original BFT protocol, and in particular, their probability distributions. We argue that faithfulness is ensured by a forward simulation. We show how to faithfully simulate any BFT protocol that uses public coins and shared objects, like common coins.

Subject Classification

ACM Subject Classification
  • Theory of computation → Distributed computing models
  • Computing methodologies → Distributed algorithms
  • General and reference → Verification
  • Byzantine failures
  • Hyperproperties
  • Forward Simulation


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