82 Search Results for "Tucci-Piergiovanni, Sara"

Volume

LIPIcs, Volume 361

29th International Conference on Principles of Distributed Systems (OPODIS 2025)

OPODIS 2025, Iaşi, Romania, December 3-5, 2025

Editors: Andrei Arusoaie, Emanuel Onica, Michael Spear, and Sara Tucci-Piergiovanni

Volume

OASIcs, Volume 101

5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

FAB 2022, June 3, 2022, Berkeley, CA, USA

Editors: Sara Tucci-Piergiovanni and Natacha Crooks

Volume

OASIcs, Volume 71

International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2019)

Tokenomics 2019, May 6-7, 2019, Paris, France

Editors: Vincent Danos, Maurice Herlihy, Maria Potop-Butucaru, Julien Prat, and Sara Tucci-Piergiovanni

Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2025
LIPIcs, Volume 361, OPODIS 2025, Complete Volume

Authors: Andrei Arusoaie, Emanuel Onica, Michael Spear, and Sara Tucci-Piergiovanni

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
LIPIcs, Volume 361, OPODIS 2025, Complete Volume
Cite as

29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 1-680, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@Proceedings{arusoaie_et_al:LIPIcs.OPODIS.2025,
  title =	{{LIPIcs, Volume 361, OPODIS 2025, Complete Volume}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{1--680},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025},
  URN =		{urn:nbn:de:0030-drops-252834},
  doi =		{10.4230/LIPIcs.OPODIS.2025},
  annote =	{Keywords: LIPIcs, Volume 361, OPODIS 2025, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2025.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Andrei Arusoaie, Emanuel Onica, Michael Spear, and Sara Tucci-Piergiovanni

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 0:i-0:xiv, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{arusoaie_et_al:LIPIcs.OPODIS.2025.0,
  author =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{0:i--0:xiv},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.0},
  URN =		{urn:nbn:de:0030-drops-252827},
  doi =		{10.4230/LIPIcs.OPODIS.2025.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.22
Making Democracy Work: Fixing and Simplifying Egalitarian Paxos

Authors: Fedor Ryabinin, Alexey Gotsman, and Pierre Sutra

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
Classical state-machine replication protocols, such as Paxos, rely on a distinguished leader process to order commands. Unfortunately, this approach makes the leader a single point of failure and increases the latency for clients that are not co-located with it. As a response to these drawbacks, Egalitarian Paxos [Iulian Moraru et al., 2013] introduced an alternative, leaderless approach, that allows replicas to order commands collaboratively. Not relying on a single leader allows the protocol to maintain non-zero throughput with up to f crashes of any processes out of a total of n = 2f+1. The protocol furthermore allows any process to execute a command c fast, in 2 message delays, provided no more than e = ⌈(f+1)/2⌉ other processes fail, and all concurrently submitted commands commute with c; the latter condition is often satisfied in practical systems. Egalitarian Paxos has served as a foundation for many other replication protocols. But unfortunately, the protocol is very complex, ambiguously specified and suffers from nontrivial bugs. In this paper, we present EPaxos* - a simpler and correct variant of Egalitarian Paxos. Our key technical contribution is a simpler failure-recovery algorithm, which we have rigorously proved correct. Our protocol also generalizes Egalitarian Paxos to cover the whole spectrum of failure thresholds f and e such that n ≥ max{2e+f-1, 2f+1} - the number of processes that we show to be optimal.
Cite as

Fedor Ryabinin, Alexey Gotsman, and Pierre Sutra. Making Democracy Work: Fixing and Simplifying Egalitarian Paxos. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 22:1-22:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{ryabinin_et_al:LIPIcs.OPODIS.2025.22,
  author =	{Ryabinin, Fedor and Gotsman, Alexey and Sutra, Pierre},
  title =	{{Making Democracy Work: Fixing and Simplifying Egalitarian Paxos}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{22:1--22:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.22},
  URN =		{urn:nbn:de:0030-drops-251955},
  doi =		{10.4230/LIPIcs.OPODIS.2025.22},
  annote =	{Keywords: Consensus, state-machine replication, fault tolerance}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2025.1
SCONE Confidential Computing Environment: Protecting Applications Against Powerful Adversaries (Invited Talk)

Authors: Christof Fetzer

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
Our objective is to protect the code, data, and keys of applications against all users with access to the computer systems. In some domains (e.g., healthcare domain), this must be guaranteed, even if the application is not entirely correct. To simplify the adoption of confidential computing, SCONE transforms cloud-native applications into confidential cloud-native applications running on vanilla Kubernetes clusters. The applications can run on Intel SGX, Intel TDX, and AMD SEV. In the near future, SCONE will also support confidential GPUs. The confidentiality, integrity, and consistency of an application’s data and keys are guaranteed by always keeping the data encrypted, i.e., at rest, in transit, and in use. This enables us to add a protection layer around applications to prevent data loss caused be bugs and backdoors in the application code.
Cite as

Christof Fetzer. SCONE Confidential Computing Environment: Protecting Applications Against Powerful Adversaries (Invited Talk). In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{fetzer:LIPIcs.OPODIS.2025.1,
  author =	{Fetzer, Christof},
  title =	{{SCONE Confidential Computing Environment: Protecting Applications Against Powerful Adversaries}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.1},
  URN =		{urn:nbn:de:0030-drops-251743},
  doi =		{10.4230/LIPIcs.OPODIS.2025.1},
  annote =	{Keywords: trusted execution environments, security}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2025.2
From Principles to Practice: Algorithmic Insights from Building the Internet Computer (Invited Talk)

Authors: Yvonne-Anne Pignolet

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
The theoretical bedrock of distributed computing rests on foundational primitives: peer-to-peer protocols, Byzantine fault tolerance, state machine replication. But what happens when these principles are stretched to a global, evolving, decentralized compute platform intended to host arbitrary applications? For the past seven years, our work has been dedicated to answering that question through the Internet Computer (IC), a public blockchain network designed for large-scale, general-purpose computation. The IC acts as a stateful serverless cloud[Maksym Arutyunyan et al., 2023], running over 900K applications for millions of users by implementing the Internet Computer Protocol (ICP)[Jan Camenisch et al., 2022] in a sharded, Byzantine-fault-tolerant setup. This talk explores the algorithmic insights gained from this journey. We will confront where our cherished theoretical models were challenged and had to be radically adapted, composed, or re-imagined. Specifically, we will dive into core problems like: - Scalable orchestration: Asynchronous and trustless composition of independent state machines. - Taming Non-Determinism: Designing protocols that allow deterministic replicated state machines to securely query external data. - The Paradox of Immutability: Enabling stateful upgrades for decentralized applications and even the underlying protocol stack without sacrificing security. I will share the successful design patterns that emerged, detail which core protocols stood the test of time, and which others we overhauled. Finally, I will discuss the hard and sometimes surprising trade-offs we made and pose open research questions to address when designing the next generation of decentralized systems.
Cite as

Yvonne-Anne Pignolet. From Principles to Practice: Algorithmic Insights from Building the Internet Computer (Invited Talk). In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{pignolet:LIPIcs.OPODIS.2025.2,
  author =	{Pignolet, Yvonne-Anne},
  title =	{{From Principles to Practice: Algorithmic Insights from Building the Internet Computer}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.2},
  URN =		{urn:nbn:de:0030-drops-251756},
  doi =		{10.4230/LIPIcs.OPODIS.2025.2},
  annote =	{Keywords: Internet Computer Protocol, blockchain, state machine replication, Byzantine fault tolerance}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2025.3
Computing with Content-Oblivious Messages (Invited Talk)

Authors: Giuseppe Antonio Di Luna

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
One of the core aspects of distributed computing is the design of algorithms that tolerate failures [Cachin et al., 2011; Raynal, 2018]. Failures may involve processes (in which case we may encounter crash-stop, memory corruption, or Byzantine failures) or the communication among processes. When processes communicate through message passing, failures may include message loss, message addition (either duplication or fabrication), and message corruption [Santoro and Widmayer, 1989]. Tight bounds are known for agreement in the synchronous setting under these types of failures [Santoro and Widmayer, 1989], and numerous works have investigated message loss in the synchronous setting and asynchronous setting for many other problems [Herlihy et al., 2013; Raynal, 2018; Santoro and Widmayer, 1990; Schmid et al., 2009]. In this talk, we focus on what can be computed when the system is asynchronous and messages may be corrupted; that is, a sent message can be arbitrarily modified by an adversary, but it cannot be deleted or duplicated. We specifically consider the bleak scenario in which all messages sent by processes are corrupted. Alternatively, one can view this as a setting where all messages have zero size, consisting only of simple pulses. This content-oblivious model is reminiscent of the beeping model [A. Casteigts et al., 2019], but in the beeping model, synchrony allows silence to be used as a means of communication. Surprisingly, contrary to what one might expect at first glance, [Censor-Hillel et al., 2023] has recently shown that, in the content-oblivious setting, when a predetermined leader is present and the network topology is 2-connected, it is possible to simulate an environment that is completely fault-free. While [Censor-Hillel et al., 2023] has shown that 2-connectivity is necessary, it also conjectured that the presence of a leader was a required assumption. [Frei et al., 2024] disproved this conjecture for the special case of oriented ring graphs by presenting a composable leader election algorithm. This result was later extended in [Chalopin et al., 2025] to the case of unoriented graphs, and, under the mild assumption of an upper bound on the network size, for any 2-edge-connected network. Thus, for the special case of ring topologies, we have a computational equivalence between content-oblivious and classic asynchronous message passing. Always in oriented in rings [Chalopin et al., 2025] has shown a non-uniform leader election algorithm with an optimal dependency on process IDs. The talk will discuss these results, focusing on the open problems and the current state of computation in systems where messages carry no content.
Cite as

Giuseppe Antonio Di Luna. Computing with Content-Oblivious Messages (Invited Talk). In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 3:1-3:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{diluna:LIPIcs.OPODIS.2025.3,
  author =	{Di Luna, Giuseppe Antonio},
  title =	{{Computing with Content-Oblivious Messages}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{3:1--3:2},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.3},
  URN =		{urn:nbn:de:0030-drops-251766},
  doi =		{10.4230/LIPIcs.OPODIS.2025.3},
  annote =	{Keywords: Fault-Tolerance, Message Failures, Simulation, Leader Election, Uniform Algorithms, Non-Uniform Algorithms}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.4
A Hierarchy of Unrestricted Deterministic Objects with Consensus Number 1

Authors: Warren Zhu

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
The consensus number of a shared object is the maximum number of processes that can solve consensus in a wait-free manner using copies of the object and registers. In 2016, to prove that an object is not fully characterized by its consensus number, Afek, Ellen and Gafni showed that for all integers n ≥ 2, there exists an infinite sequence of deterministic objects of consensus number n with strictly increasing computational power. In 2018, Daian, Losa, Afek, and Gafni constructed an infinite sequence of deterministic objects of consensus number 1 with strictly decreasing computational power, but the single operation that each of these objects supports is restricted in how it can be used during an execution. As restrictions can have an effect on an object’s consensus number, it was left as an open question whether the same result holds without this restriction. In this paper, we construct an infinite sequence of unrestricted deterministic objects with strictly decreasing computational power. All objects in this sequence have consensus number 1.
Cite as

Warren Zhu. A Hierarchy of Unrestricted Deterministic Objects with Consensus Number 1. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 4:1-4:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{zhu:LIPIcs.OPODIS.2025.4,
  author =	{Zhu, Warren},
  title =	{{A Hierarchy of Unrestricted Deterministic Objects with Consensus Number 1}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{4:1--4:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.4},
  URN =		{urn:nbn:de:0030-drops-251778},
  doi =		{10.4230/LIPIcs.OPODIS.2025.4},
  annote =	{Keywords: Shared Memory, Wait-free, Set Agreement, Consensus Hierarchy}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.5
Tight Conditions for Binary-Output Tasks Under Crashes

Authors: Timothé Albouy, Antonio Fernández Anta, Chryssis Georgiou, Nicolas Nicolaou, and Junlang Wang

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
This paper explores necessary and sufficient system conditions to solve distributed tasks with binary outputs (i.e., tasks with output values in {0,1}). We focus on the distinct output sets of values a task can produce (intentionally disregarding validity and value multiplicity), considering that some processes may output no value. In a distributed system with n processes, of which up to t ≤ n can crash, we provide a complete characterization of the tight conditions on n and t under which every class of tasks with binary outputs is solvable, for both synchronous and asynchronous systems. This output-set approach yields highly general results: it unifies multiple distributed computing problems, such as binary consensus and symmetry breaking, and it produces impossibility proofs that hold for stronger task formulations, including those that consider validity, account for value multiplicity, or move beyond binary outputs.
Cite as

Timothé Albouy, Antonio Fernández Anta, Chryssis Georgiou, Nicolas Nicolaou, and Junlang Wang. Tight Conditions for Binary-Output Tasks Under Crashes. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 5:1-5:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{albouy_et_al:LIPIcs.OPODIS.2025.5,
  author =	{Albouy, Timoth\'{e} and Fern\'{a}ndez Anta, Antonio and Georgiou, Chryssis and Nicolaou, Nicolas and Wang, Junlang},
  title =	{{Tight Conditions for Binary-Output Tasks Under Crashes}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{5:1--5:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.5},
  URN =		{urn:nbn:de:0030-drops-251786},
  doi =		{10.4230/LIPIcs.OPODIS.2025.5},
  annote =	{Keywords: Distributed solvability, Asynchrony, Synchrony, Impossibility proofs, Binary-output tasks, Crash tolerance, Disagreement}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.6
Foundations of Fiat-Denominated Loans Collateralized by Cryptocurrencies

Authors: Pavel Hubáček, Jan Václavek, and Michelle Yeo

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
The rising importance of cryptocurrencies as financial assets pushed their applicability from an object of speculation closer to standard financial instruments such as loans. In this work, we initiate the study of secure protocols that enable fiat-denominated loans collateralized by cryptocurrencies such as Bitcoin. We provide limited-custodial protocols for such loans relying only on trusted arbitration and provide their game-theoretical analysis. We also highlight various interesting directions for future research.
Cite as

Pavel Hubáček, Jan Václavek, and Michelle Yeo. Foundations of Fiat-Denominated Loans Collateralized by Cryptocurrencies. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 6:1-6:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{hubacek_et_al:LIPIcs.OPODIS.2025.6,
  author =	{Hub\'{a}\v{c}ek, Pavel and V\'{a}clavek, Jan and Yeo, Michelle},
  title =	{{Foundations of Fiat-Denominated Loans Collateralized by Cryptocurrencies}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{6:1--6:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.6},
  URN =		{urn:nbn:de:0030-drops-251796},
  doi =		{10.4230/LIPIcs.OPODIS.2025.6},
  annote =	{Keywords: Blockchains, Cryptocurrencies, DeFi, Loans, Mechanism design, Subgame Perfect Equilibrium, Rational analysis}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.7
Mobile Byzantine Agreement in a Trusted World

Authors: Bo Pan and Maria Potop-Butucaru

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
In this paper, we address the Byzantine Agreement problem in synchronous systems where Byzantine agents can move from process to process, corrupting their host. We focus on two representative models: Garay’s and Buhrman’s models. In Garay’s model, when a process has been left by the Byzantine agent, it enters a cured state, is aware of its condition, and can remain silent for a round to prevent the dissemination of incorrect information. In Buhrman’s model, a Byzantine agent moves together with the message. It has been shown that solving Byzantine Agreement requires at least 4t + 1 processes in Garay’s model, and at least 3t + 1 in Buhrman’s model. In this paper, we aim to increase the tolerance to mobile Byzantine agents by integrating a trusted counter abstraction into both models. This abstraction prevents nodes from equivocating. In the new models, we prove that at least 3t+1, respectively 2t+1 processors are needed to tolerate t mobile Byzantine agents. Furthermore, we propose novel Mobile Byzantine Agreement algorithms that match these new lower bounds for both Garay’s and Buhrman’s models, achieving agreement in 𝒪(n) synchronous rounds.
Cite as

Bo Pan and Maria Potop-Butucaru. Mobile Byzantine Agreement in a Trusted World. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 7:1-7:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{pan_et_al:LIPIcs.OPODIS.2025.7,
  author =	{Pan, Bo and Potop-Butucaru, Maria},
  title =	{{Mobile Byzantine Agreement in a Trusted World}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{7:1--7:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.7},
  URN =		{urn:nbn:de:0030-drops-251809},
  doi =		{10.4230/LIPIcs.OPODIS.2025.7},
  annote =	{Keywords: Byzantine Agreement, Mobile Faults, Trusted Abstractions}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.8
Weaker Assumptions for Asymmetric Trust

Authors: Ignacio Amores-Sesar, Christian Cachin, Simon Holmgaard Kamp, and Juan Villacis

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
In distributed systems with asymmetric trust, each participant is free to make its own trust assumptions about others, captured by an asymmetric quorum system. This contrasts with ordinary, symmetric quorum systems and threshold models, where trust assumptions are uniformly shared among participants. Fundamental problems like reliable broadcast and consensus are unsolvable in the asymmetric model if quorum systems satisfy only the classical properties of consistency and availability. Existing approaches overcome this by introducing stronger assumptions. We show that some of these assumptions are overly restrictive, so much so that they effectively eliminate the benefits of asymmetric trust. To address this, we propose a new approach to characterize asymmetric problems and, building upon it, present algorithms for reliable broadcast and consensus that require weaker assumptions than previous solutions. Our methods are general and can be extended to other core problems in systems with asymmetric trust.
Cite as

Ignacio Amores-Sesar, Christian Cachin, Simon Holmgaard Kamp, and Juan Villacis. Weaker Assumptions for Asymmetric Trust. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

Copy BibTex To Clipboard

@InProceedings{amoressesar_et_al:LIPIcs.OPODIS.2025.8,
  author =	{Amores-Sesar, Ignacio and Cachin, Christian and Kamp, Simon Holmgaard and Villacis, Juan},
  title =	{{Weaker Assumptions for Asymmetric Trust}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{8:1--8:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.8},
  URN =		{urn:nbn:de:0030-drops-251812},
  doi =		{10.4230/LIPIcs.OPODIS.2025.8},
  annote =	{Keywords: Asymmetric Trust, Quorum Systems, Reliable Broadcast, Consensus}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2025.9
Contention-Aware Cooperation

Authors: Timothé Albouy, Davide Frey, Mathieu Gestin, Michel Raynal, and François Taïani

Published in: LIPIcs, Volume 361, 29th International Conference on Principles of Distributed Systems (OPODIS 2025)

Abstract
As shown by Reliable Broadcast and Consensus, cooperation among a set of independent computing entities (sequential processes) is crucial in fault-tolerant distributed computing. Considering n-process asynchronous message-passing systems where some processes may be Byzantine, this paper introduces a novel cooperation abstraction, Contention-Aware Cooperation (CAC). While Reliable Broadcast is a one-to-n cooperation abstraction and Consensus is an n-to-n cooperation abstraction, CAC is a d-to-n cooperation abstraction where d (1 ≤ d ≤ n) varies with each run and remains unknown to the processes. Correct processes accept the same set of 𝓁 pairs ⟨ v,i ⟩ (v is the value proposed by p_i) from the d proposer processes, where 1 ≤ 𝓁 ≤ d and (as d) 𝓁 remains unknown to the processes (except in specific cases). Those 𝓁 values are accepted one at a time, potentially in different orders at each process. In addition, CAC provides each process with an imperfect oracle that provides insights into the values that they may accept in the future. Interestingly, the CAC abstraction is particularly efficient in favorable circumstances, when the oracle becomes accurate, which processes can detect. To illustrate its practical utility, the paper details two applications leveraging CAC: a fast consensus implementation optimized for low contention (named Cascading Consensus), and a novel naming problem that can be solved under full asynchrony. All algorithms presented require signatures.
Cite as

Timothé Albouy, Davide Frey, Mathieu Gestin, Michel Raynal, and François Taïani. Contention-Aware Cooperation. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 9:1-9:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

Copy BibTex To Clipboard

@InProceedings{albouy_et_al:LIPIcs.OPODIS.2025.9,
  author =	{Albouy, Timoth\'{e} and Frey, Davide and Gestin, Mathieu and Raynal, Michel and Ta\"{i}ani, Fran\c{c}ois},
  title =	{{Contention-Aware Cooperation}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{9:1--9:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.9},
  URN =		{urn:nbn:de:0030-drops-251823},
  doi =		{10.4230/LIPIcs.OPODIS.2025.9},
  annote =	{Keywords: Agreement, Asynchronous message-passing system, Byzantine processes, Conflict detection, Consensus, Cooperation abstraction, Distributed computing, Fault tolerance, Optimistically terminating consensus, Short-naming}
}
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