30 Search Results for "Kuznetsov, Petr"

Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2025.45
Brief Announcement: DAGs for the Masses

Authors: Michael Anoprenko, Andrei Tonkikh, Alexander Spiegelman, and Petr Kuznetsov

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
A recent approach to building consensus protocols on top of Directed Acyclic Graphs (DAGs) shows much promise due to its simplicity and stable throughput. However, as each node in the DAG typically includes a linear number of references to the nodes in the previous round, prior DAG protocols only scale up to a certain point when the overhead of maintaining the graph becomes the bottleneck. To enable large-scale deployments of DAG-based protocols, we propose a sparse DAG architecture, where each node includes only a constant number of references to random nodes in the previous round. We present a sparse version of Bullshark - one of the most prominent DAG-based consensus protocols - and demonstrate its improved scalability. Remarkably, unlike other protocols that use random sampling to reduce communication complexity, we manage to avoid sacrificing resilience: the protocol can tolerate up to f < n/3 Byzantine faults (where n is the number of participants), same as its less scalable deterministic counterpart. The proposed "sparse" methodology can be applied to any protocol that maintains disseminated system updates and causal relations between them in a graph-like structure. Our simulations show that the considerable reduction of transmitted metadata in sparse DAGs results in more efficient network utilization and better scalability.
Cite as

Michael Anoprenko, Andrei Tonkikh, Alexander Spiegelman, and Petr Kuznetsov. Brief Announcement: DAGs for the Masses. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 45:1-45:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{anoprenko_et_al:LIPIcs.DISC.2025.45,
  author =	{Anoprenko, Michael and Tonkikh, Andrei and Spiegelman, Alexander and Kuznetsov, Petr},
  title =	{{Brief Announcement: DAGs for the Masses}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{45:1--45:7},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.45},
  URN =		{urn:nbn:de:0030-drops-248617},
  doi =		{10.4230/LIPIcs.DISC.2025.45},
  annote =	{Keywords: Consensus, Atomic Broadcast, Byzantine Fault Tolerance, DAGs, Scalability, Sampling}
}
Document
DOI: 10.4230/LIPIcs.DISC.2025.15
Asynchronous Latency and Fast Atomic Snapshot

Authors: João Paulo Bezerra, Luciano Freitas, Petr Kuznetsov, and Matthieu Rambaud

Published in: LIPIcs, Volume 356, 39th International Symposium on Distributed Computing (DISC 2025)

Abstract
This paper introduces a novel, fast atomic-snapshot protocol for asynchronous message-passing systems. In the process of defining what "fast" means exactly, we spot a few interesting issues that arise when conventional time metrics are applied to long-lived asynchronous algorithms. We reveal some gaps in latency claims made in earlier work on snapshot algorithms, which hamper their comparative time-complexity analysis. We then come up with a new unifying time-complexity metric that captures the latency of an operation in an asynchronous, long-lived implementation. This allows us to formally grasp latency improvements of our atomic-snapshot algorithm with respect to the state-of-the-art protocols: optimal latency in fault-free runs without contention, short constant latency in fault-free runs with contention, the worst-case latency proportional to the number of active concurrent failures, and constant amortized latency.
Cite as

João Paulo Bezerra, Luciano Freitas, Petr Kuznetsov, and Matthieu Rambaud. Asynchronous Latency and Fast Atomic Snapshot. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 15:1-15:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bezerra_et_al:LIPIcs.DISC.2025.15,
  author =	{Bezerra, Jo\~{a}o Paulo and Freitas, Luciano and Kuznetsov, Petr and Rambaud, Matthieu},
  title =	{{Asynchronous Latency and Fast Atomic Snapshot}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{15:1--15:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-402-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{356},
  editor =	{Kowalski, Dariusz R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2025.15},
  URN =		{urn:nbn:de:0030-drops-248326},
  doi =		{10.4230/LIPIcs.DISC.2025.15},
  annote =	{Keywords: Asynchronous systems, time complexity, atomic snapshot, crash faults}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.3
Fast, Private and Regulated Payments in Asynchronous Networks

Authors: Maxence Brugeres, Victor Languille, Petr Kuznetsov, and Hamza Zarfaoui

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
We propose a decentralized asset-transfer system that enjoys full privacy: no party can learn the details of a transaction, except for its issuer and its recipient. Furthermore, the recipient is not aware of the sender’s identity. Our system does not rely on consensus or synchrony assumptions, and therefore, it is responsive, since it runs at the actual network speed. Under the hood, every transaction creates a consumable coin equipped with a non-interactive zero-knowledge proof (NIZK) that confirms that the issuer has sufficient funds without revealing any information about her identity, the recipient’s identity, or the payment amount. Moreover, we equip our system with a regulatory enforcement mechanism that can be used to regulate transfer limits or restrict specific addresses from sending or receiving funds, while preserving the system’s privacy guarantees. Finally, we report on PaxPay, our implementation of Fully Private Asset Transfer (FPAT) that uses the Gnark library for the NIZKs. In our benchmark, PaxPay exhibits better performance than earlier proposals that either ensure only partial privacy, require some kind of network synchrony or do not implement regulation features. Our system thus reconciles privacy, responsiveness, regulation enforcement and performance.
Cite as

Maxence Brugeres, Victor Languille, Petr Kuznetsov, and Hamza Zarfaoui. Fast, Private and Regulated Payments in Asynchronous Networks. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 3:1-3:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{brugeres_et_al:LIPIcs.AFT.2025.3,
  author =	{Brugeres, Maxence and Languille, Victor and Kuznetsov, Petr and Zarfaoui, Hamza},
  title =	{{Fast, Private and Regulated Payments in Asynchronous Networks}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{3:1--3:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025.3},
  URN =		{urn:nbn:de:0030-drops-247227},
  doi =		{10.4230/LIPIcs.AFT.2025.3},
  annote =	{Keywords: Anonymous, Asset Transfer, Asynchronous System, BFT, CBDC, NIZK, Payment System, Privacy, Regulation, Scalability, zk-SNARK}
}
Document
DOI: 10.4230/LIPIcs.ESA.2025.85
A Simple yet Exact Analysis of the MultiQueue

Authors: Stefan Walzer and Marvin Williams

Published in: LIPIcs, Volume 351, 33rd Annual European Symposium on Algorithms (ESA 2025)

Abstract
The MultiQueue is a relaxed concurrent priority queue consisting of n internal priority queues, where an insertion uses a random queue and a deletion considers two random queues and deletes the minimum from the one with the smaller minimum. The rank error of the deletion is the number of smaller elements in the MultiQueue. Alistarh et al. [Alistarh et al., 2017] have demonstrated in a sophisticated potential argument that the expected rank error remains bounded by 𝒪(n) over long sequences of deletions. In this paper we present a simpler analysis by identifying the stable distribution of an underlying Markov chain and with it the long-term distribution of the rank error exactly. Simple calculations then reveal the expected long-term rank error to be (5/6)n-1+1/(6n). Our arguments generalize to deletion schemes where the probability to delete from a given queue depends only on the rank of the queue. Specifically, this includes deleting from the best of c randomly selected queues for any c > 1.
Cite as

Stefan Walzer and Marvin Williams. A Simple yet Exact Analysis of the MultiQueue. In 33rd Annual European Symposium on Algorithms (ESA 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 351, pp. 85:1-85:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{walzer_et_al:LIPIcs.ESA.2025.85,
  author =	{Walzer, Stefan and Williams, Marvin},
  title =	{{A Simple yet Exact Analysis of the MultiQueue}},
  booktitle =	{33rd Annual European Symposium on Algorithms (ESA 2025)},
  pages =	{85:1--85:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-395-9},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{351},
  editor =	{Benoit, Anne and Kaplan, Haim and Wild, Sebastian and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2025.85},
  URN =		{urn:nbn:de:0030-drops-245533},
  doi =		{10.4230/LIPIcs.ESA.2025.85},
  annote =	{Keywords: MultiQueue, concurrent data structure, stochastic process, Markov chain}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2025.17
Just Verification of Mutual Exclusion Algorithms

Authors: Rob van Glabbeek, Bas Luttik, and Myrthe S. C. Spronck

Published in: LIPIcs, Volume 348, 36th International Conference on Concurrency Theory (CONCUR 2025)

Abstract
We verify the correctness of a variety of mutual exclusion algorithms through model checking. We look at algorithms where communication is via shared read/write registers, where those registers can be atomic or non-atomic. For the verification of liveness properties, it is necessary to assume a completeness criterion to eliminate spurious counterexamples. We use justness as completeness criterion. Justness depends on a concurrency relation; we consider several such relations, modelling different assumptions on the working of the shared registers. We present executions demonstrating the violation of correctness properties by several algorithms, and in some cases suggest improvements.
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Rob van Glabbeek, Bas Luttik, and Myrthe S. C. Spronck. Just Verification of Mutual Exclusion Algorithms. In 36th International Conference on Concurrency Theory (CONCUR 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 348, pp. 17:1-17:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{vanglabbeek_et_al:LIPIcs.CONCUR.2025.17,
  author =	{van Glabbeek, Rob and Luttik, Bas and Spronck, Myrthe S. C.},
  title =	{{Just Verification of Mutual Exclusion Algorithms}},
  booktitle =	{36th International Conference on Concurrency Theory (CONCUR 2025)},
  pages =	{17:1--17:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-389-8},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{348},
  editor =	{Bouyer, Patricia and van de Pol, Jaco},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2025.17},
  URN =		{urn:nbn:de:0030-drops-239670},
  doi =		{10.4230/LIPIcs.CONCUR.2025.17},
  annote =	{Keywords: Mutual exclusion, safe registers, regular registers, overlapping reads and writes, atomicity, safety, liveness, starvation freedom, justness, model checking, mCRL2}
}
Document
Media Exposition
DOI: 10.4230/LIPIcs.SoCG.2025.81
AmoebotSim 2.0: A Visual Simulation Environment for the Amoebot Model with Reconfigurable Circuits and Joint Movements (Media Exposition)

Authors: Matthias Artmann, Tobias Maurer, Andreas Padalkin, Daniel Warner, and Christian Scheideler

Published in: LIPIcs, Volume 332, 41st International Symposium on Computational Geometry (SoCG 2025)

Abstract
We present AmoebotSim 2.0, a simulation environment for the geometric amoebot model of programmable matter that supports the reconfigurable circuit and joint movement extensions of the model. In the geometric amoebot model, we consider systems of simple computational entities called amoebots in a regular triangular grid environment. We are interested in distributed algorithms that solve coordination and shape formation problems. The reconfigurable circuit and joint movement extensions of the model allow the amoebots to communicate over greater distances and perform more complex movements, overcoming some limitations of the original model. AmoebotSim 2.0 is an open-source simulation environment that supports these extensions and provides a rich graphical interface, flexible simulation features, an extensive API, and comprehensive documentation.
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Matthias Artmann, Tobias Maurer, Andreas Padalkin, Daniel Warner, and Christian Scheideler. AmoebotSim 2.0: A Visual Simulation Environment for the Amoebot Model with Reconfigurable Circuits and Joint Movements (Media Exposition). In 41st International Symposium on Computational Geometry (SoCG 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 332, pp. 81:1-81:5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{artmann_et_al:LIPIcs.SoCG.2025.81,
  author =	{Artmann, Matthias and Maurer, Tobias and Padalkin, Andreas and Warner, Daniel and Scheideler, Christian},
  title =	{{AmoebotSim 2.0: A Visual Simulation Environment for the Amoebot Model with Reconfigurable Circuits and Joint Movements}},
  booktitle =	{41st International Symposium on Computational Geometry (SoCG 2025)},
  pages =	{81:1--81:5},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-370-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{332},
  editor =	{Aichholzer, Oswin and Wang, Haitao},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2025.81},
  URN =		{urn:nbn:de:0030-drops-232338},
  doi =		{10.4230/LIPIcs.SoCG.2025.81},
  annote =	{Keywords: Programmable matter, amoebot model, reconfigurable circuits, joint movements, simulator}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.14
Near-Optimal Communication Byzantine Reliable Broadcast Under a Message Adversary

Authors: Timothé Albouy, Davide Frey, Ran Gelles, Carmit Hazay, Michel Raynal, Elad Michael Schiller, François Taïani, and Vassilis Zikas

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
We address the problem of Reliable Broadcast in asynchronous message-passing systems with n nodes, of which up to t are malicious (faulty), in addition to a message adversary that can drop some of the messages sent by correct (non-faulty) nodes. We present a Message-Adversary-Tolerant Byzantine Reliable Broadcast (MBRB) algorithm that communicates O(|m|+nκ) bits per node, where |m| represents the length of the application message and κ = Ω(log n) is a security parameter. This communication complexity is optimal up to the parameter κ. This significantly improves upon the state-of-the-art MBRB solution (Albouy, Frey, Raynal, and Taïani, TCS 2023), which incurs communication of O(n|m|+n²κ) bits per node. Our solution sends at most 4n² messages overall, which is asymptotically optimal. Reduced communication is achieved by employing coding techniques that replace the need for all nodes to (re-)broadcast the entire application message m. Instead, nodes forward authenticated fragments of the encoding of m using an erasure-correcting code. Under the cryptographic assumptions of threshold signatures and vector commitments, and assuming n > 3t+2d, where the adversary drops at most d messages per broadcast, our algorithm allows at least 𝓁 = n - t - (1 + ε)d (for any arbitrarily low ε > 0) correct nodes to reconstruct m, despite missing fragments caused by the malicious nodes and the message adversary.
Cite as

Timothé Albouy, Davide Frey, Ran Gelles, Carmit Hazay, Michel Raynal, Elad Michael Schiller, François Taïani, and Vassilis Zikas. Near-Optimal Communication Byzantine Reliable Broadcast Under a Message Adversary. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 14:1-14:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{albouy_et_al:LIPIcs.OPODIS.2024.14,
  author =	{Albouy, Timoth\'{e} and Frey, Davide and Gelles, Ran and Hazay, Carmit and Raynal, Michel and Schiller, Elad Michael and Ta\"{i}ani, Fran\c{c}ois and Zikas, Vassilis},
  title =	{{Near-Optimal Communication Byzantine Reliable Broadcast Under a Message Adversary}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{14:1--14:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.14},
  URN =		{urn:nbn:de:0030-drops-225503},
  doi =		{10.4230/LIPIcs.OPODIS.2024.14},
  annote =	{Keywords: Asynchronous message-passing, Byzantine fault-tolerance, Message adversary, Reliable broadcast, Erasure-correction codes, \{Threshold\} signatures, \{Vector commitments\}}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.15
Quit-Resistant Reliable Broadcast and Efficient Terminating Gather

Authors: Mose Mizrahi Erbes and Roger Wattenhofer

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
Termination is a central property in distributed computing. A party terminates a protocol once it stops accepting and sending messages. We discover that byzantine reliable broadcast is sometimes used in a manner which leads to non-terminating protocols. We consider an asynchronous network of n parties up to t of which are byzantine, and show that if each party is to broadcast its value and terminate upon obtaining n - t values, then composing n parallel reliable broadcast instances leads to non-termination. The issue is that a party must quit t broadcast instances early in order to terminate, a behaviour not supported by ordinary reliable broadcast. So, we modify Bracha’s protocol into a quit-resistant reliable broadcast (QBRB) protocol which lets the parties quit early. This protocol retains its termination guarantees as long as no party quits before some party terminates. Then, we turn our attention to Gather, an all-to-all broadcast primitive which guarantees that the parties obtain n - t common values. Existing error-free deterministic Gather protocols either run forever, or fail to terminate since the parties quit reliable broadcast instances. We design an error-free, deterministic, terminating (and binding) Gather protocol for 𝓁-bit inputs with the communication complexity 𝒪(𝓁 n² + n³log n). This matches the state-of-the-art for non-terminating Gather. Finally, inspired by our QBRB protocol, we design a reliable broadcast protocol which retains its termination guarantees no matter when any party quits. To achieve this, we give each party the option to output ⊥ if more than q parties quit before some party terminates. The protocol requires 4t + q < n, which is optimal, and it lets parties quit after they have suffered transient crash failures so that they can help the remaining parties terminate.
Cite as

Mose Mizrahi Erbes and Roger Wattenhofer. Quit-Resistant Reliable Broadcast and Efficient Terminating Gather. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 15:1-15:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{mizrahierbes_et_al:LIPIcs.OPODIS.2024.15,
  author =	{Mizrahi Erbes, Mose and Wattenhofer, Roger},
  title =	{{Quit-Resistant Reliable Broadcast and Efficient Terminating Gather}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{15:1--15:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.15},
  URN =		{urn:nbn:de:0030-drops-225519},
  doi =		{10.4230/LIPIcs.OPODIS.2024.15},
  annote =	{Keywords: Asynchronous networks, byzantine fault tolerance, protocol termination, reliable broadcast, all-to-all broadcast, gather}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.16
Byzantine Reliable Broadcast with Low Communication and Time Complexity

Authors: Thomas Locher

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
Byzantine reliable broadcast is a fundamental problem in distributed computing, which has been studied extensively over the past decades. State-of-the-art algorithms are predominantly based on the approach to share encoded fragments of the broadcast message, yielding an asymptotically optimal communication complexity when the message size exceeds the network size, a condition frequently encountered in practice. However, algorithms following the standard coding approach incur an overhead factor of at least 3, which can already be a burden for bandwidth-constrained applications. Minimizing this overhead is an important objective with immediate benefits to protocols that use a reliable broadcast routine as a building block. This paper introduces a novel mechanism to lower the communication and computational complexity. Two algorithms are presented that employ this mechanism to reliably broadcast messages in an asynchronous network where less than a third of all nodes are Byzantine. The first algorithm reduces the overhead factor to 2 and has a time complexity of 3 if the sender is honest, whereas the second algorithm attains an optimal time complexity of 2 with the same overhead factor in the absence of equivocation. Moreover, an optimization is proposed that reduces the overhead factor to 3/2 under normal operation in practice. Lastly, a lower bound is proved that an overhead factor lower than 3/2 cannot be achieved for a relevant class of reliable broadcast algorithms.
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Thomas Locher. Byzantine Reliable Broadcast with Low Communication and Time Complexity. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 16:1-16:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{locher:LIPIcs.OPODIS.2024.16,
  author =	{Locher, Thomas},
  title =	{{Byzantine Reliable Broadcast with Low Communication and Time Complexity}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{16:1--16:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.16},
  URN =		{urn:nbn:de:0030-drops-225524},
  doi =		{10.4230/LIPIcs.OPODIS.2024.16},
  annote =	{Keywords: Asynchronous Networks, Reliable Broadcast, Communication Complexity}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.31
Dynamic Probabilistic Reliable Broadcast

Authors: João Paulo Bezerra, Veronika Anikina, Petr Kuznetsov, Liron Schiff, and Stefan Schmid

Published in: LIPIcs, Volume 324, 28th International Conference on Principles of Distributed Systems (OPODIS 2024)

Abstract
Byzantine reliable broadcast is a fundamental primitive in distributed systems that allows a set of processes to agree on a message broadcast by a dedicated process, even when some of them are malicious (Byzantine). It guarantees that no two correct processes deliver different messages, and if a message is delivered by a correct process, every correct process eventually delivers one. Byzantine reliable broadcast protocols are known to scale poorly, as they require Ω(n²) message exchanges, where n is the number of system members. The quadratic cost can be explained by the inherent need for every process to relay a message to every other process. In this paper, we explore ways to overcome this limitation by casting the problem to the probabilistic setting. We propose a solution in which every broadcast message is validated by a small set of witnesses, which allows us to maintain low latency and small communication complexity. In order to tolerate the slow adaptive adversary, we dynamically select the witnesses through a novel stream-local hash function: given a stream of inputs, it generates a stream of output hashed values that adapts to small deviations of the inputs. Our performance analysis shows that the proposed solution exhibits significant scalability gains over state-of-the-art protocols.
Cite as

João Paulo Bezerra, Veronika Anikina, Petr Kuznetsov, Liron Schiff, and Stefan Schmid. Dynamic Probabilistic Reliable Broadcast. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 31:1-31:30, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bezerra_et_al:LIPIcs.OPODIS.2024.31,
  author =	{Bezerra, Jo\~{a}o Paulo and Anikina, Veronika and Kuznetsov, Petr and Schiff, Liron and Schmid, Stefan},
  title =	{{Dynamic Probabilistic Reliable Broadcast}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{31:1--31:30},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-360-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{324},
  editor =	{Bonomi, Silvia and Galletta, Letterio and Rivi\`{e}re, Etienne and Schiavoni, Valerio},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2024.31},
  URN =		{urn:nbn:de:0030-drops-225679},
  doi =		{10.4230/LIPIcs.OPODIS.2024.31},
  annote =	{Keywords: Reliable broadcast, probabilistic algorithms, witness sets, stream-local hashing, cryptocurrencies, accountability}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2023.31
A Tight Bound on Multiple Spending in Decentralized Cryptocurrencies

Authors: João Paulo Bezerra and Petr Kuznetsov

Published in: LIPIcs, Volume 286, 27th International Conference on Principles of Distributed Systems (OPODIS 2023)

Abstract
The last decade has seen a variety of Asset-Transfer systems designed for decentralized environments. The major problem these systems address is double-spending, and solving it inherently imposes strong trust assumptions on the system participants. In this paper, we take a non-orthodox approach to the double-spending problem that might suit better realistic environments in which these systems are to be deployed. We consider the decentralized trust setting, where each user may independently choose who to trust by forming their local quorums. In this setting, we define k-Spending Asset Transfer, a relaxed version of asset transfer which bounds the number of times a system participant may spend an asset it received. We establish a precise relationship between the decentralized trust assumptions and k, the optimal spending number of the system.
Cite as

João Paulo Bezerra and Petr Kuznetsov. A Tight Bound on Multiple Spending in Decentralized Cryptocurrencies. In 27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, pp. 31:1-31:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bezerra_et_al:LIPIcs.OPODIS.2023.31,
  author =	{Bezerra, Jo\~{a}o Paulo and Kuznetsov, Petr},
  title =	{{A Tight Bound on Multiple Spending in Decentralized Cryptocurrencies}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{31:1--31:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-308-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{286},
  editor =	{Bessani, Alysson and D\'{e}fago, Xavier and Nakamura, Junya and Wada, Koichi and Yamauchi, Yukiko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2023.31},
  URN =		{urn:nbn:de:0030-drops-195210},
  doi =		{10.4230/LIPIcs.OPODIS.2023.31},
  annote =	{Keywords: Quorum systems, decentralized trust, consistency measure, asset transfer, accountability}
}
Document
Vision
DOI: 10.4230/TGDK.1.1.6
Towards Ordinal Data Science

Authors: Gerd Stumme, Dominik Dürrschnabel, and Tom Hanika

Published in: TGDK, Volume 1, Issue 1 (2023): Special Issue on Trends in Graph Data and Knowledge. Transactions on Graph Data and Knowledge, Volume 1, Issue 1

Abstract
Order is one of the main instruments to measure the relationship between objects in (empirical) data. However, compared to methods that use numerical properties of objects, the amount of ordinal methods developed is rather small. One reason for this is the limited availability of computational resources in the last century that would have been required for ordinal computations. Another reason - particularly important for this line of research - is that order-based methods are often seen as too mathematically rigorous for applying them to real-world data. In this paper, we will therefore discuss different means for measuring and ‘calculating’ with ordinal structures - a specific class of directed graphs - and show how to infer knowledge from them. Our aim is to establish Ordinal Data Science as a fundamentally new research agenda. Besides cross-fertilization with other cornerstone machine learning and knowledge representation methods, a broad range of disciplines will benefit from this endeavor, including, psychology, sociology, economics, web science, knowledge engineering, scientometrics.
Cite as

Gerd Stumme, Dominik Dürrschnabel, and Tom Hanika. Towards Ordinal Data Science. In Special Issue on Trends in Graph Data and Knowledge. Transactions on Graph Data and Knowledge (TGDK), Volume 1, Issue 1, pp. 6:1-6:39, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Article{stumme_et_al:TGDK.1.1.6,
  author =	{Stumme, Gerd and D\"{u}rrschnabel, Dominik and Hanika, Tom},
  title =	{{Towards Ordinal Data Science}},
  journal =	{Transactions on Graph Data and Knowledge},
  pages =	{6:1--6:39},
  ISSN =	{2942-7517},
  year =	{2023},
  volume =	{1},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/TGDK.1.1.6},
  URN =		{urn:nbn:de:0030-drops-194801},
  doi =		{10.4230/TGDK.1.1.6},
  annote =	{Keywords: Order relation, data science, relational theory of measurement, metric learning, general algebra, lattices, factorization, approximations and heuristics, factor analysis, visualization, browsing, explainability}
}
Document
DOI: 10.4230/LIPIcs.DISC.2022.24
Distributed Randomness from Approximate Agreement

Authors: Luciano Freitas, Petr Kuznetsov, and Andrei Tonkikh

Published in: LIPIcs, Volume 246, 36th International Symposium on Distributed Computing (DISC 2022)

Abstract
Randomisation is a critical tool in designing distributed systems. The common coin primitive, enabling the system members to agree on an unpredictable random number, has proven to be particularly useful. We observe, however, that it is impossible to implement a truly random common coin protocol in a fault-prone asynchronous system. To circumvent this impossibility, we introduce two relaxations of the perfect common coin: (1) approximate common coin generating random numbers that are close to each other; and (2) Monte Carlo common coin generating a common random number with an arbitrarily small, but non-zero, probability of failure. Building atop the approximate agreement primitive, we obtain efficient asynchronous implementations of the two abstractions, tolerating up to one third of Byzantine processes. Our protocols do not assume trusted setup or public key infrastructure and converge to the perfect coin exponentially fast in the protocol running time. By plugging one of our protocols for Monte Carlo common coin in a well-known consensus algorithm, we manage to get a binary Byzantine agreement protocol with O(n³ log n) communication complexity, resilient against an adaptive adversary, and tolerating the optimal number f < n/3 of failures without trusted setup or PKI. To the best of our knowledge, the best communication complexity for binary Byzantine agreement achieved so far in this setting is O(n⁴). We also show how the approximate common coin, combined with a variant of Gray code, can be used to solve an interesting problem of Intersecting Random Subsets, which we introduce in this paper.
Cite as

Luciano Freitas, Petr Kuznetsov, and Andrei Tonkikh. Distributed Randomness from Approximate Agreement. In 36th International Symposium on Distributed Computing (DISC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 246, pp. 24:1-24:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{freitas_et_al:LIPIcs.DISC.2022.24,
  author =	{Freitas, Luciano and Kuznetsov, Petr and Tonkikh, Andrei},
  title =	{{Distributed Randomness from Approximate Agreement}},
  booktitle =	{36th International Symposium on Distributed Computing (DISC 2022)},
  pages =	{24:1--24:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-255-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{246},
  editor =	{Scheideler, Christian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2022.24},
  URN =		{urn:nbn:de:0030-drops-172157},
  doi =		{10.4230/LIPIcs.DISC.2022.24},
  annote =	{Keywords: Asynchronous, approximate agreement, weak common coin, consensus, Byzantine agreement}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2021.2
Accountable Distributed Computing (Invited Talk)

Authors: Petr Kuznetsov

Published in: LIPIcs, Volume 217, 25th International Conference on Principles of Distributed Systems (OPODIS 2021)

Abstract
There are two major ways to deal with failures in distributed computing: fault-tolerance and accountability. Fault-tolerance intends to anticipate failures by investing into replication and synchronization, so that the system’s correctness is not affected by faulty components. In contrast, accountability enables detecting failures a posteriori and raising undeniable evidences against faulty components. In this talk, we discuss how accountability can be achieved, both in generic and application-specific ways. We begin with an overview of fault detection mechanisms used in benign, crash-prone system, with a focus on the weakest failure detector question. We then consider the fault detection problem in systems with general, Byzantine failures and explore which classes of misbehavior can be detected and which - cannot. We then study the mechanism of application-specific accountability that, intuitively, only accounts for instances of misbehavior that affect particular correctness criteria. Finally, we discuss how fault detection can be combined with reconfiguration, opening an avenue of "self-healing" systems that seamlessly replace faulty system components with correct ones.
Cite as

Petr Kuznetsov. Accountable Distributed Computing (Invited Talk). In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{kuznetsov:LIPIcs.OPODIS.2021.2,
  author =	{Kuznetsov, Petr},
  title =	{{Accountable Distributed Computing}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-219-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{217},
  editor =	{Bramas, Quentin and Gramoli, Vincent and Milani, Alessia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2021.2},
  URN =		{urn:nbn:de:0030-drops-157775},
  doi =		{10.4230/LIPIcs.OPODIS.2021.2},
  annote =	{Keywords: Fault-tolerance, fault detection, accountability, application-specific}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2021.23
RandSolomon: Optimally Resilient Random Number Generator with Deterministic Termination

Authors: Luciano Freitas de Souza, Andrei Tonkikh, Sara Tucci-Piergiovanni, Renaud Sirdey, Oana Stan, Nicolas Quero, and Petr Kuznetsov

Published in: LIPIcs, Volume 217, 25th International Conference on Principles of Distributed Systems (OPODIS 2021)

Abstract
Multi-party random number generation is a key building-block in many practical protocols. While straightforward to solve when all parties are trusted to behave correctly, the problem becomes much more difficult in the presence of faults. This paper presents RandSolomon, a partially synchronous protocol that allows a system of N processes to produce an unpredictable common random number shared by correct participants. The protocol is optimally resilient, as it allows up to f = ⌊(N-1)/3⌋ of the processes to behave arbitrarily, ensures deterministic termination and, contrary to prior solutions, does not, at any point, expect faulty processes to be responsive.
Cite as

Luciano Freitas de Souza, Andrei Tonkikh, Sara Tucci-Piergiovanni, Renaud Sirdey, Oana Stan, Nicolas Quero, and Petr Kuznetsov. RandSolomon: Optimally Resilient Random Number Generator with Deterministic Termination. In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, pp. 23:1-23:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{freitasdesouza_et_al:LIPIcs.OPODIS.2021.23,
  author =	{Freitas de Souza, Luciano and Tonkikh, Andrei and Tucci-Piergiovanni, Sara and Sirdey, Renaud and Stan, Oana and Quero, Nicolas and Kuznetsov, Petr},
  title =	{{RandSolomon: Optimally Resilient Random Number Generator with Deterministic Termination}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{23:1--23:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-219-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{217},
  editor =	{Bramas, Quentin and Gramoli, Vincent and Milani, Alessia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2021.23},
  URN =		{urn:nbn:de:0030-drops-157986},
  doi =		{10.4230/LIPIcs.OPODIS.2021.23},
  annote =	{Keywords: Byzantine Fault Tolerance, Partially Synchronous, Deterministic Termination, Randomness Beacon, Multi Party Computation, BFT-RNG}
}
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