Colordag: An Incentive-Compatible Blockchain

Authors Ittai Abraham, Danny Dolev, Ittay Eyal, Joseph Y. Halpern

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Author Details

Ittai Abraham
  • Intel Labs, Haifa, Israel
Danny Dolev
  • The Hebrew University of Jerusalem, Israel
Ittay Eyal
  • Technion, Haifa, Israel
Joseph Y. Halpern
  • Cornell University, Ithaca, NY, USA


We thank Roi Bar-Zur for comments on an early version of this manuscript, and the reviewers of the paper for their helpful comments.

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Ittai Abraham, Danny Dolev, Ittay Eyal, and Joseph Y. Halpern. Colordag: An Incentive-Compatible Blockchain. In 37th International Symposium on Distributed Computing (DISC 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 281, pp. 1:1-1:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


We present Colordag, a blockchain protocol where following the prescribed strategy is, with high probability, a best response as long as all miners have less than 1/2 of the mining power. We prove the correctness of Colordag even if there is an extremely powerful adversary who knows future actions of the scheduler: specifically, when agents will generate blocks and when messages will arrive. The state-of-the-art protocol, Fruitchain, is an ε-Nash equilibrium as long as all miners have less than 1/2 of the mining power. However, there is a simple deviation that guarantees that deviators are never worse off than they would be by following Fruitchain, and can sometimes do better. Thus, agents are motivated to deviate. Colordag implements a solution concept that we call ε-sure Nash equilibrium and does not suffer from this problem. Because it is an ε-sure Nash equilibrium, Colordag is an ε-Nash equilibrium and with probability 1-ε is a best response.

Subject Classification

ACM Subject Classification
  • Computing methodologies → Distributed computing methodologies
  • Theory of computation → Solution concepts in game theory
  • Security and privacy → Distributed systems security
  • Game theory
  • incentives
  • blockchain


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