Formal Modeling and Verification of the Algorand Consensus Protocol in CADP

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Main Authors: Esposito, Andrea, Rossi, Francesco P., Bernardo, Marco, Fabris, Francesco, Garavel, Hubert
Format: Preprint
Published: 2025
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author Esposito, Andrea
Rossi, Francesco P.
Bernardo, Marco
Fabris, Francesco
Garavel, Hubert
author_facet Esposito, Andrea
Rossi, Francesco P.
Bernardo, Marco
Fabris, Francesco
Garavel, Hubert
contents Algorand is a scalable and secure permissionless blockchain that achieves proof-of-stake consensus via cryptographic self-sortition and binary Byzantine agreement. In this paper we present a process algebraic model of the Algorand consensus protocol with the aim of enabling formal verification. Our model captures the behavior of participants in terms of the structured alternation of consensus steps toward a committee-based agreement. We validate the correctness of the protocol in the absence of adversaries and then extend our model to assess the influence of coordinated malicious nodes that can force the commit of an empty block instead of the proposed one. The adversarial scenario is analyzed through an equivalence-checking-based noninterference framework that we have implemented in the CADP verification toolkit. In addition to highlighting both the robustness and the limitations of the Algorand protocol under adversarial assumptions, this work illustrates the added value of using formal methods for the analysis of consensus algorithms within blockchains.
format Preprint
id arxiv_https___arxiv_org_abs_2508_19452
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Formal Modeling and Verification of the Algorand Consensus Protocol in CADP
Esposito, Andrea
Rossi, Francesco P.
Bernardo, Marco
Fabris, Francesco
Garavel, Hubert
Distributed, Parallel, and Cluster Computing
Algorand is a scalable and secure permissionless blockchain that achieves proof-of-stake consensus via cryptographic self-sortition and binary Byzantine agreement. In this paper we present a process algebraic model of the Algorand consensus protocol with the aim of enabling formal verification. Our model captures the behavior of participants in terms of the structured alternation of consensus steps toward a committee-based agreement. We validate the correctness of the protocol in the absence of adversaries and then extend our model to assess the influence of coordinated malicious nodes that can force the commit of an empty block instead of the proposed one. The adversarial scenario is analyzed through an equivalence-checking-based noninterference framework that we have implemented in the CADP verification toolkit. In addition to highlighting both the robustness and the limitations of the Algorand protocol under adversarial assumptions, this work illustrates the added value of using formal methods for the analysis of consensus algorithms within blockchains.
title Formal Modeling and Verification of the Algorand Consensus Protocol in CADP
topic Distributed, Parallel, and Cluster Computing
url https://arxiv.org/abs/2508.19452