40 Search Results for "Hillel, Eshcar"

Volume

LIPIcs, Volume 253

26th International Conference on Principles of Distributed Systems (OPODIS 2022)

OPODIS 2022, December 13-15, 2022, Brussels, Belgium

Editors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Document
DOI: 10.4230/LIPIcs.DISC.2025.6
Hierarchical Consensus: Scalability Through Optimism and Weak Liveness

Authors: Pedro Antonino, Antoine Durand, and A. W. Roscoe

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

Abstract
Scalability is a central concern of Byzantine Fault Tolerant (BFT) distributed protocols. The ubiquitous approach to work around the well-known Dolev-Reischuk Ω(n²) communication complexity lower bound is to use a random selection process to draw a hopefully small committee from a population of agents to run the communication-heavy protocol. We propose a notion of hierarchical consensus that combines two sub-protocols: an optimistic primary sub-protocol that can tolerate less than 1/2 failures and a fallback secondary protocol that can tolerate less than 1/3 failures; we achieve the higher failure threshold by requiring a weaker notion of liveness for the primary. This distinction between the level of fault tolerance between primary and secondary is reflected in the size of committees implementing these protocols. For a population of agents with close to 2/3 of honest agents, we need to select a committee with hundreds of agents to reach the level of tolerance expected for the primary, whereas we need thousands to reach the level expected for the secondary with a very small probability of error ε. Our hierarchical construct is such that if the primary comes to a decision, it can simply propagate it to the secondary protocol, so it does not need to properly engage in an agreement protocol independently. Our architecture is flexible and allows us to use our technique for most protocols that are based on random sampling. By studying hierarchical protocols, we discovered new theoretical results of independent interest. Specifically, the ability to handover from a primary protocol requires a new Justifiability property that allows agents to pre-decide on a value, such that if the protocol decides, it must be on that pre-decided value.
Cite as

Pedro Antonino, Antoine Durand, and A. W. Roscoe. Hierarchical Consensus: Scalability Through Optimism and Weak Liveness. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 6:1-6:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{antonino_et_al:LIPIcs.DISC.2025.6,
  author =	{Antonino, Pedro and Durand, Antoine and Roscoe, A. W.},
  title =	{{Hierarchical Consensus: Scalability Through Optimism and Weak Liveness}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{6:1--6:20},
  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.2025.6},
  URN =		{urn:nbn:de:0030-drops-248232},
  doi =		{10.4230/LIPIcs.DISC.2025.6},
  annote =	{Keywords: Hierarchical, Handover, Justifiability, Consensus, Distributed Systems, Blockchain}
}
Document
DOI: 10.4230/LIPIcs.DISC.2025.32
Coordination Through Stochastic Channels

Authors: Pierre Fraigniaud, Boaz Patt-Shamir, and Sergio Rajsbaum

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

Abstract
We consider a stochastic network model consisting of a set of n synchronous processes communicating by message passing. In each round, processes send messages directly to each other over a complete communication graph. The processes do not fail, but messages can be lost. Each message is delivered with probability p, for a given parameter p ∈ [0,1]. We study the following optimization version of approximate agreement in this model. We assume that processes start with binary input values, execute an algorithm for a fixed number of rounds, and decide values in [0,1] satisfying the usual validity requirement stating that if all processes start with the same input value, then they should all decide that value. We propose deterministic algorithms that minimize the expected discrepancy, namely, the expected maximum distance between the decided values. We also present lower bounds on the expected discrepancy, which demonstrate the optimality of our algorithms for two processes. Finally, we present applications of our algorithms to solve randomized consensus and randomized approximate agreement.
Cite as

Pierre Fraigniaud, Boaz Patt-Shamir, and Sergio Rajsbaum. Coordination Through Stochastic Channels. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 32:1-32:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{fraigniaud_et_al:LIPIcs.DISC.2025.32,
  author =	{Fraigniaud, Pierre and Patt-Shamir, Boaz and Rajsbaum, Sergio},
  title =	{{Coordination Through Stochastic Channels}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{32:1--32:19},
  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.2025.32},
  URN =		{urn:nbn:de:0030-drops-248493},
  doi =		{10.4230/LIPIcs.DISC.2025.32},
  annote =	{Keywords: Approximate agreement, randomized consensus, stochastic models, topology}
}
Document
DOI: 10.4230/LIPIcs.DISC.2025.27
On the h-Majority Dynamics with Many Opinions

Authors: Francesco d'Amore, Niccolò D'Archivio, George Giakkoupis, and Emanuele Natale

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

Abstract
We present the first upper bound on the convergence time to consensus of the well-known h-majority dynamics with k opinions, in the synchronous setting, for h and k that are both non-constant values. We suppose that, at the beginning of the process, there is some initial additive bias towards some plurality opinion, that is, there is an opinion that is supported by x nodes while any other opinion is supported by strictly fewer nodes. We prove that, with high probability, if the bias is ω(√x) and the initial plurality opinion is supported by at least x = ω(log n) nodes, then the process converges to plurality consensus in O(log n) rounds whenever h = ω(n log n / x). A main corollary is the following: if k = o(n / log n) and the process starts from an almost-balanced configuration with an initial bias of magnitude ω(√{n/k}) towards the initial plurality opinion, then any function h = ω(k log n) suffices to guarantee convergence to consensus in O(log n) rounds, with high probability. Our upper bound shows that the lower bound of Ω(k / h²) rounds to reach consensus given by Becchetti et al. (2017) cannot be pushed further than Ω̃(k / h). Moreover, the bias we require is asymptotically smaller than the Ω(√{nlog n}) bias that guarantees plurality consensus in the 3-majority dynamics: in our case, the required bias is at most any (arbitrarily small) function in ω(√x) for any value of k ≥ 2.
Cite as

Francesco d'Amore, Niccolò D'Archivio, George Giakkoupis, and Emanuele Natale. On the h-Majority Dynamics with Many Opinions. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 27:1-27:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{damore_et_al:LIPIcs.DISC.2025.27,
  author =	{d'Amore, Francesco and D'Archivio, Niccol\`{o} and Giakkoupis, George and Natale, Emanuele},
  title =	{{On the h-Majority Dynamics with Many Opinions}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{27:1--27:24},
  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.2025.27},
  URN =		{urn:nbn:de:0030-drops-248448},
  doi =		{10.4230/LIPIcs.DISC.2025.27},
  annote =	{Keywords: Distributed Algorithms, Randomized Algorithms, Markov Chains, Consensus Problem, Opinion dynamics, Plurality Consensus}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.14
Optimistic Message Dissemination

Authors: Chen-Da Liu-Zhang, Christian Matt, and Søren Eller Thomsen

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

Abstract
Message dissemination is a fundamental building block in distributed systems and guarantees that any message sent eventually reaches all parties. State of the art provably secure protocols for disseminating messages have a per-party communication complexity that is linear in the inverse of the fraction of parties that are guaranteed to be honest in the worst case. Unfortunately, this per-party communication complexity arises even in cases where the actual fraction of parties that behave honestly is close to 1. In this paper, we propose an optimistic message dissemination protocol that adopts to the actual conditions in which it is deployed, with optimal worst-case per-party communication complexity. Our protocol cuts the complexity of prior provably secure protocols for 49% worst-case corruption almost in half under optimistic conditions and allows practitioners to combine efficient heuristics with secure fallback mechanisms.
Cite as

Chen-Da Liu-Zhang, Christian Matt, and Søren Eller Thomsen. Optimistic Message Dissemination. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 14:1-14:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{liuzhang_et_al:LIPIcs.AFT.2025.14,
  author =	{Liu-Zhang, Chen-Da and Matt, Christian and Thomsen, S{\o}ren Eller},
  title =	{{Optimistic Message Dissemination}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{14:1--14:24},
  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.2025.14},
  URN =		{urn:nbn:de:0030-drops-247332},
  doi =		{10.4230/LIPIcs.AFT.2025.14},
  annote =	{Keywords: flooding, message dissemination, optimistic}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.16
Nakamoto Consensus from Multiple Resources

Authors: Mirza Ahad Baig, Christoph U. Günther, and Krzysztof Pietrzak

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

Abstract
The blocks in the Bitcoin blockchain "record" the amount of work W that went into creating them through proofs of work. When honest parties control a majority of the work, consensus is achieved by picking the chain with the highest recorded weight. Resources other than work have been considered to secure such longest-chain blockchains. In Chia, blocks record the amount of disk-space S (via a proof of space) and sequential computational steps V (through a VDF). In this paper, we ask what weight functions Γ(S,V,W) (that assign a weight to a block as a function of the recorded space, speed, and work) are secure in the sense that whenever the weight of the resources controlled by honest parties is larger than the weight of adversarial parties, the blockchain is secure against private double-spending attacks. We completely classify such functions in an idealized "continuous" model: Γ(S,V,W) is secure against private double-spending attacks if and only if it is homogeneous of degree one in the "timed" resources V and W, i.e., αΓ(S,V,W) = Γ(S,α V, α W). This includes the Bitcoin rule Γ(S,V,W) = W and the Chia rule Γ(S,V,W) = S ⋅ V. In a more realistic model where blocks are created at discrete time-points, one additionally needs some mild assumptions on the dependency on S (basically, the weight should not grow too much if S is slightly increased, say linear as in Chia). Our classification is more general and allows various instantiations of the same resource. It provides a powerful tool for designing new longest-chain blockchains. E.g., consider combining different PoWs to counter centralization, say the Bitcoin PoW W₁ and a memory-hard PoW W₂. Previous work suggested to use W₁+W₂ as weight. Our results show that using e.g., √{W₁}⋅ √{W₂} or min{W₁,W₂} are also secure, and we argue that in practice these are much better choices.
Cite as

Mirza Ahad Baig, Christoph U. Günther, and Krzysztof Pietrzak. Nakamoto Consensus from Multiple Resources. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 16:1-16:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{baig_et_al:LIPIcs.AFT.2025.16,
  author =	{Baig, Mirza Ahad and G\"{u}nther, Christoph U. and Pietrzak, Krzysztof},
  title =	{{Nakamoto Consensus from Multiple Resources}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{16:1--16:23},
  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.2025.16},
  URN =		{urn:nbn:de:0030-drops-247353},
  doi =		{10.4230/LIPIcs.AFT.2025.16},
  annote =	{Keywords: Nakamoto Consensus, Heaviest-chain Rule, Resource Theory}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.13
Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility

Authors: Raphael Gerlach, Sören von der Gracht, Christopher Hahn, Jonas Harbig, and Peter Kling

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

Abstract
In the general pattern formation (GPF) problem, a swarm of simple autonomous, disoriented robots must form a given pattern. The robots' simplicity imply a strong limitation: When the initial configuration is rotationally symmetric, only patterns with a similar symmetry can be formed [Masafumi Yamashita and Ichiro Suzuki, 2010]. The only known algorithm to form large patterns with limited visibility and without memory requires the robots to start in a near-gathering (a swarm of constant diameter) [Christopher Hahn et al., 2024]. However, not only do we not know any near-gathering algorithm guaranteed to preserve symmetry but most natural gathering strategies trivially increase symmetries [Jannik Castenow et al., 2022]. Thus, we study near-gathering without changing the swarm’s rotational symmetry for disoriented, oblivious robots with limited visibility (the OBLOT-model, see [Paola Flocchini et al., 2019]). We introduce a technique based on the theory of dynamical systems to analyze how a given algorithm affects symmetry and provide sufficient conditions for symmetry preservation. Until now, it was unknown whether the considered OBLOT-model allows for any non-trivial algorithm that always preserves symmetry. Our first result shows that a variant of Go-To-The-Average always preserves symmetry but may sometimes lead to multiple, unconnected near-gathering clusters. Our second result is a symmetry-preserving near-gathering algorithm that works on swarms with a convex boundary (the outer boundary of the unit disc graph) and without "holes" (circles of diameter 1 inside the boundary without any robots).
Cite as

Raphael Gerlach, Sören von der Gracht, Christopher Hahn, Jonas Harbig, and Peter Kling. Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 13:1-13:28, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gerlach_et_al:LIPIcs.OPODIS.2024.13,
  author =	{Gerlach, Raphael and von der Gracht, S\"{o}ren and Hahn, Christopher and Harbig, Jonas and Kling, Peter},
  title =	{{Symmetry Preservation in Swarms of Oblivious Robots with Limited Visibility}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{13:1--13:28},
  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.2024.13},
  URN =		{urn:nbn:de:0030-drops-225490},
  doi =		{10.4230/LIPIcs.OPODIS.2024.13},
  annote =	{Keywords: Swarm Algorithm, Swarm Robots, Distributed Algorithm, Pattern Formation, Limited Visibility, Oblivious}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.19
A General Class of Reductions and Extension-Based Proofs

Authors: Yusong Shi and Weidong Liu

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

Abstract
The concept of extension-based proofs models the idea of a valency argument which is widely used in distributed computing. Extension-based proofs have been shown to be limited in power: there is no extension-based proof of the impossibility of a wait-free protocol for (n,k)-set agreement among n > k ≥ 2 processes. Previous work used a restricted class of reductions to show that there are no extension-based proofs of the impossibility of wait-free protocols for some other distributed computing problems. It is known that for a restricted class of reductions, if a task 𝒯 reduces to 𝒮 and 𝒯 has an augmented extension-based proof that it is impossible to solve in the NIS model, then so does 𝒮. We introduce multiple-instance extension-based proofs and show that, if 𝒯 reduces to multiple instances of 𝒮, instead of just one instance and 𝒯 has an augmented extension-based proof, then 𝒮 has a multiple-instance extension-based proof that it is impossible to solve in the NIIS model. We introduce a new version of extension-based proofs that can further our understanding of extension-based proofs and their limitations.
Cite as

Yusong Shi and Weidong Liu. A General Class of Reductions and Extension-Based Proofs. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 19:1-19:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{shi_et_al:LIPIcs.OPODIS.2024.19,
  author =	{Shi, Yusong and Liu, Weidong},
  title =	{{A General Class of Reductions and Extension-Based Proofs}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{19:1--19:17},
  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.2024.19},
  URN =		{urn:nbn:de:0030-drops-225559},
  doi =		{10.4230/LIPIcs.OPODIS.2024.19},
  annote =	{Keywords: Reductions, Impossibility proofs, Extension-based proof}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.32
Distributed Agreement in the Arrovian Framework

Authors: Kenan Wood, Hammurabi Mendes, and Jonad Pulaj

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

Abstract
Preference aggregation is a fundamental problem in voting theory, in which public input rankings of a set of alternatives (called preferences) must be aggregated into a single preference that satisfies certain soundness properties. The celebrated Arrow Impossibility Theorem is equivalent to a distributed task in a synchronous fault-free system that satisfies properties such as respecting unanimous preferences, maintaining independence of irrelevant alternatives (IIA), and non-dictatorship, along with consensus since only one preference can be decided. In this work, we study a weaker distributed task in which crash faults are introduced, IIA is not required, and the consensus property is relaxed to either k-set agreement or ε-approximate agreement using any metric on the set of preferences. In particular, we prove several novel impossibility results for both of these tasks in both synchronous and asynchronous distributed systems. We additionally show that the impossibility for our ε-approximate agreement task using the Kendall tau or Spearman footrule metrics holds under extremely weak assumptions.
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Kenan Wood, Hammurabi Mendes, and Jonad Pulaj. Distributed Agreement in the Arrovian Framework. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 32:1-32:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wood_et_al:LIPIcs.OPODIS.2024.32,
  author =	{Wood, Kenan and Mendes, Hammurabi and Pulaj, Jonad},
  title =	{{Distributed Agreement in the Arrovian Framework}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{32:1--32:18},
  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.2024.32},
  URN =		{urn:nbn:de:0030-drops-225686},
  doi =		{10.4230/LIPIcs.OPODIS.2024.32},
  annote =	{Keywords: Approximate Agreement, Set Agreement, Preference Aggregation, Voting Theory, Impossibility}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.8
Optimal Multilevel Slashing for Blockchains

Authors: Kenan Wood, Hammurabi Mendes, and Jonad Pulaj

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

Abstract
We present the notion of multilevel slashing, where proof-of-stake blockchain validators can obtain gradual levels of assurance that a certain block is bound to be finalized in a global consensus procedure, unless an increasing and optimally large number of Byzantine processes have their staked assets slashed - that is, deducted - due to provably incorrect behavior. Our construction is a highly parameterized generalization of combinatorial intersection systems based on finite projective spaces, with asymptotic high availability and optimal slashing properties. Even under weak conditions, we show that our construction has asymptotically optimal slashing properties with respect to message complexity and validator load; this result also illustrates a fundamental trade off between message complexity, load, and slashing. In addition, we show that any intersection system whose ground elements are disjoint subsets of nodes (e.g. "committees" in committee-based consensus protocols) has asymptotic high availability under similarly weak conditions. Finally, our multilevel construction gives the flexibility to blockchain validators to decide how many "levels" of finalization assurance they wish to obtain. This functionality can be seen either as (i) a form of an early, slashing-based block finalization; or (ii) a service to support reorg tolerance.
Cite as

Kenan Wood, Hammurabi Mendes, and Jonad Pulaj. Optimal Multilevel Slashing for Blockchains. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{wood_et_al:LIPIcs.OPODIS.2024.8,
  author =	{Wood, Kenan and Mendes, Hammurabi and Pulaj, Jonad},
  title =	{{Optimal Multilevel Slashing for Blockchains}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{8:1--8:18},
  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.2024.8},
  URN =		{urn:nbn:de:0030-drops-225445},
  doi =		{10.4230/LIPIcs.OPODIS.2024.8},
  annote =	{Keywords: Blockchains, Finality, Slashablility, Committees, Availability}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2022
LIPIcs, Volume 253, OPODIS 2022, Complete Volume

Authors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
LIPIcs, Volume 253, OPODIS 2022, Complete Volume
Cite as

26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 1-536, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Proceedings{hillel_et_al:LIPIcs.OPODIS.2022,
  title =	{{LIPIcs, Volume 253, OPODIS 2022, Complete Volume}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{1--536},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022},
  URN =		{urn:nbn:de:0030-drops-176190},
  doi =		{10.4230/LIPIcs.OPODIS.2022},
  annote =	{Keywords: LIPIcs, Volume 253, OPODIS 2022, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2022.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Eshcar Hillel, Roberto Palmieri, and Etienne Rivière

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

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

26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 0:i-0:xiv, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{hillel_et_al:LIPIcs.OPODIS.2022.0,
  author =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{0:i--0:xiv},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.0},
  URN =		{urn:nbn:de:0030-drops-176203},
  doi =		{10.4230/LIPIcs.OPODIS.2022.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.1
Theory Meets Practice in the Algorand Blockchain (Invited Talk)

Authors: Victor Luchangco

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Robust and effective distributed systems require good theory and good engineering, not separately but in concert: user requirements and system constraints are not merely implementation details but often must inform the design of algorithms for such systems. Blockchains are an excellent example. The heart of a blockchain is its (Byzantine) consensus protocol, and consensus protocols have been extensively studied in the theory community for decades. But traditional consensus protocols are not directly applicable to blockchains, which have, or hope to have, millions of participants. Furthermore, public blockchains, which allow anyone to participate, must have some mechanism to guarantee the security of the protocol, and traditional fault models do not adequately capture the assumptions of such mechanisms. In this talk, I will discuss these and other ways in which theory and practice meet in the context of the Algorand blockchain, and how Algorand is able to achieve high transaction throughput with low latency.
Cite as

Victor Luchangco. Theory Meets Practice in the Algorand Blockchain (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{luchangco:LIPIcs.OPODIS.2022.1,
  author =	{Luchangco, Victor},
  title =	{{Theory Meets Practice in the Algorand Blockchain}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.1},
  URN =		{urn:nbn:de:0030-drops-176219},
  doi =		{10.4230/LIPIcs.OPODIS.2022.1},
  annote =	{Keywords: Theory and practice, Design of distributed systems, Blockchain, Consensus, Algorand}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.2
Recoverable Computing (Invited Talk)

Authors: Panagiota Fatourou

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
Non-Volatile Memory (NVM) is an emerging memory technology which aims to address the high computational demands of modern applications and support recovery from crashes. Recovery ensures that after a crash every executed operation is able to recover and return a correct response. This talk will shed light on different aspects of the question "How does concurrent computing change in systems with NVM and what will the impact of persistent memory be on the way we compute?". Specifically, this talk addresses the following four main challenges in NVM computing. - Challenge 1: How to appropriately model and abstract fundamental aspects of NVM computing? The talk will provide an overview of the theoretical framework for NVM computing, including a discussion of correctness conditions, progress guarantees, failure types, etc. - Challenge 2: How to compute in a recoverable way at no significant cost? The talk will summarize state-of-the-art generic approaches for deriving recoverable synchronization algorithms, as well as recoverable implementations of many widely-used concurrent data structures on top of them. The collection of data structures includes fundamental structures, such as stacks and queues, but also more complex structures that implement sets, such as linked-lists and trees. - Challenge 3: How to analyze the cost of recoverable algorithms? The talk will present a way of analyzing the cost of persistence instructions, not by simply counting them but by separating them into categories based on the impact they have on the performance. This analysis reveals that understanding the actual persistence cost of an algorithm in machines with NVM, is more complicated than previously thought, and requires a thorough evaluation, since the performance impact of different persistence instructions may greatly vary. - Challenge 4: When is Recoverable Consensus Harder Than Consensus? The talk will briefly discuss the ability of different shared object types to solve recoverable consensus using NVM when processes crash and recover, and it will compare the difficulty of solving recoverable consensus to the difficulty of solving the standard consensus problem in a system with halting failures. For each of the above challenges, the talk will present main results, provide some of the details of the best-performing techniques, and discuss open problems and directions for further research. Some of the results that will be discussed in detail have appeared in [Attiya et al., 2022; Delporte-Gallet et al., 2022; Fatourou et al., 2022].
Cite as

Panagiota Fatourou. Recoverable Computing (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 2:1-2:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{fatourou:LIPIcs.OPODIS.2022.2,
  author =	{Fatourou, Panagiota},
  title =	{{Recoverable Computing}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{2:1--2:2},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.2},
  URN =		{urn:nbn:de:0030-drops-176221},
  doi =		{10.4230/LIPIcs.OPODIS.2022.2},
  annote =	{Keywords: non-volatile memory, persistence, detectability, durability, recoverable algorithms, recoverable data structures, persistent objects, stacks, queues, heaps, synchronization, universal constructions, software combining, lock-freedom, wait-freedom, persistence cost analysis}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.OPODIS.2022.3
Realistic Self-Stabilization (Invited Talk)

Authors: Sébastien Tixeuil

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)

Abstract
It is almost fifty years since Dijkstra coined the term "self-stabilization" to denote a distributed system able to recover correct behavior starting from any arbitrary (even unreachable) configuration. His seminal paper triggered many works since then, exploring over the years new variants of the original concept, new application domains, and new complexity results. While the huge majority of those contributions relates to theory, considering computability and worst case complexity issues, this talk revisits old and recent contributions from the prism of "realistic" distributed systems, aiming to address the following question: is self-stabilization relevant in practice for distributed systems?
Cite as

Sébastien Tixeuil. Realistic Self-Stabilization (Invited Talk). In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, p. 3:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{tixeuil:LIPIcs.OPODIS.2022.3,
  author =	{Tixeuil, S\'{e}bastien},
  title =	{{Realistic Self-Stabilization}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{3:1--3:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.3},
  URN =		{urn:nbn:de:0030-drops-176232},
  doi =		{10.4230/LIPIcs.OPODIS.2022.3},
  annote =	{Keywords: Self-stabilization, Distributed systems, Probable stabilization, Performance evaluation, Asynchronous message passing, Multi-tolerance}
}
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