47 Search Results for "Friedman, Roy"

Volume

LIPIcs, Volume 153

23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

OPODIS 2019, December 17-19, 2019, Neuchâtel, Switzerland

Editors: Pascal Felber, Roy Friedman, Seth Gilbert, and Avery Miller

Document
DOI: 10.4230/LIPIcs.CCC.2024.18
Pseudorandomness, Symmetry, Smoothing: I

Authors: Harm Derksen, Peter Ivanov, Chin Ho Lee, and Emanuele Viola

Published in: LIPIcs, Volume 300, 39th Computational Complexity Conference (CCC 2024)

Abstract
We prove several new results about bounded uniform and small-bias distributions. A main message is that, small-bias, even perturbed with noise, does not fool several classes of tests better than bounded uniformity. We prove this for threshold tests, small-space algorithms, and small-depth circuits. In particular, we obtain small-bias distributions that - achieve an optimal lower bound on their statistical distance to any bounded-uniform distribution. This closes a line of research initiated by Alon, Goldreich, and Mansour in 2003, and improves on a result by O'Donnell and Zhao. - have heavier tail mass than the uniform distribution. This answers a question posed by several researchers including Bun and Steinke. - rule out a popular paradigm for constructing pseudorandom generators, originating in a 1989 work by Ajtai and Wigderson. This again answers a question raised by several researchers. For branching programs, our result matches a bound by Forbes and Kelley. Our small-bias distributions above are symmetric. We show that the xor of any two symmetric small-bias distributions fools any bounded function. Hence our examples cannot be extended to the xor of two small-bias distributions, another popular paradigm whose power remains unknown. We also generalize and simplify the proof of a result of Bazzi.
Cite as

Harm Derksen, Peter Ivanov, Chin Ho Lee, and Emanuele Viola. Pseudorandomness, Symmetry, Smoothing: I. In 39th Computational Complexity Conference (CCC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 300, pp. 18:1-18:27, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{derksen_et_al:LIPIcs.CCC.2024.18,
  author =	{Derksen, Harm and Ivanov, Peter and Lee, Chin Ho and Viola, Emanuele},
  title =	{{Pseudorandomness, Symmetry, Smoothing: I}},
  booktitle =	{39th Computational Complexity Conference (CCC 2024)},
  pages =	{18:1--18:27},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-331-7},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{300},
  editor =	{Santhanam, Rahul},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2024.18},
  URN =		{urn:nbn:de:0030-drops-204144},
  doi =		{10.4230/LIPIcs.CCC.2024.18},
  annote =	{Keywords: pseudorandomness, k-wise uniform distributions, small-bias distributions, noise, symmetric tests, thresholds, Krawtchouk polynomials}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2024.73
A Characterization of Complexity in Public Goods Games

Authors: Matan Gilboa

Published in: LIPIcs, Volume 297, 51st International Colloquium on Automata, Languages, and Programming (ICALP 2024)

Abstract
We complete the characterization of the computational complexity of equilibrium in public goods games on graphs. In this model, each vertex represents an agent deciding whether to produce a public good, with utility defined by a "best-response pattern" determining the best response to any number of productive neighbors. We prove that the equilibrium problem is NP-complete for every finite non-monotone best-response pattern. This answers the open problem of [Gilboa and Nisan, 2022], and completes the answer to a question raised by [Papadimitriou and Peng, 2021], for all finite best-response patterns.
Cite as

Matan Gilboa. A Characterization of Complexity in Public Goods Games. In 51st International Colloquium on Automata, Languages, and Programming (ICALP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 297, pp. 73:1-73:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{gilboa:LIPIcs.ICALP.2024.73,
  author =	{Gilboa, Matan},
  title =	{{A Characterization of Complexity in Public Goods Games}},
  booktitle =	{51st International Colloquium on Automata, Languages, and Programming (ICALP 2024)},
  pages =	{73:1--73:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-322-5},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{297},
  editor =	{Bringmann, Karl and Grohe, Martin and Puppis, Gabriele and Svensson, Ola},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2024.73},
  URN =		{urn:nbn:de:0030-drops-202164},
  doi =		{10.4230/LIPIcs.ICALP.2024.73},
  annote =	{Keywords: Nash Equilibrium, Public Goods, Computational Complexity}
}
Document
DOI: 10.4230/DagMan.10.1.1
Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282)

Authors: James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, and Frank Wolter

Published in: Dagstuhl Manifestos, Volume 10, Issue 1 (2024)

Abstract
Knowledge Representation and Reasoning is a central, longstanding, and active area of Artificial Intelligence. Over the years it has evolved significantly; more recently it has been challenged and complemented by research in areas such as machine learning and reasoning under uncertainty. In July 2022,sser a Dagstuhl Perspectives workshop was held on Knowledge Representation and Reasoning. The goal of the workshop was to describe the state of the art in the field, including its relation with other areas, its shortcomings and strengths, together with recommendations for future progress. We developed this manifesto based on the presentations, panels, working groups, and discussions that took place at the Dagstuhl Workshop. It is a declaration of our views on Knowledge Representation: its origins, goals, milestones, and current foci; its relation to other disciplines, especially to Artificial Intelligence; and on its challenges, along with key priorities for the next decade.
Cite as

James P. Delgrande, Birte Glimm, Thomas Meyer, Miroslaw Truszczynski, and Frank Wolter. Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282). In Dagstuhl Manifestos, Volume 10, Issue 1, pp. 1-61, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@Article{delgrande_et_al:DagMan.10.1.1,
  author =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Wolter, Frank},
  title =	{{Current and Future Challenges in Knowledge Representation and Reasoning (Dagstuhl Perspectives Workshop 22282)}},
  pages =	{1--61},
  journal =	{Dagstuhl Manifestos},
  ISSN =	{2193-2433},
  year =	{2024},
  volume =	{10},
  number =	{1},
  editor =	{Delgrande, James P. and Glimm, Birte and Meyer, Thomas and Truszczynski, Miroslaw and Wolter, Frank},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagMan.10.1.1},
  URN =		{urn:nbn:de:0030-drops-201403},
  doi =		{10.4230/DagMan.10.1.1},
  annote =	{Keywords: Knowledge representation and reasoning, Applications of logics, Declarative representations, Formal logic}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2023.34
Sketching the Path to Efficiency: Lightweight Learned Cache Replacement

Authors: Rana Shahout and Roy Friedman

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

Abstract
Cache management policies are responsible for selecting the items that should be kept in the cache, and are therefore a fundamental design choice for obtaining an effective caching solution. Heuristic approaches have been used to identify access patterns that affect cache management decisions. However, their behavior is inconsistent, as they can perform well for certain access patterns and poorly for others. Given machine learning’s (ML) remarkable achievements in predicting diverse problems, ML techniques can be applied to create a cache management policy. Yet a significant challenge arises from the memory overhead associated with ML components. These components retain per item information and must be invoked on each access, contradicting the goal of minimizing the cache’s resource signature. In this work, we propose ALPS, a light-weight cache management policy that takes into account the cost of the ML component. ALPS combines ML with traditional heuristic-based approaches and facilitates learning by identifying several statistical features derived from space-efficient sketches. ALPS’s ML process derives its features from these sketches, resulting in a lightweight and highly effective meta-policy for cache management. We evaluate our approach over real-world workloads run against five popular heuristic cache management policies as well as a state-of-the-art ML-based policy. In our experiments, ALPS always obtained the best hit ratio. Specifically, ALPS improves the hit ratio compared to LRU by up to 20%, Hyperbolic by up to 31%, ARC by up to 9% and W-TinyLFU by up to 26% on various real-world workloads. Its resource requirements are orders of magnitude lower than previous ML-based approaches.
Cite as

Rana Shahout and Roy Friedman. Sketching the Path to Efficiency: Lightweight Learned Cache Replacement. In 27th International Conference on Principles of Distributed Systems (OPODIS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 286, pp. 34:1-34:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{shahout_et_al:LIPIcs.OPODIS.2023.34,
  author =	{Shahout, Rana and Friedman, Roy},
  title =	{{Sketching the Path to Efficiency: Lightweight Learned Cache Replacement}},
  booktitle =	{27th International Conference on Principles of Distributed Systems (OPODIS 2023)},
  pages =	{34:1--34:21},
  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.2023.34},
  URN =		{urn:nbn:de:0030-drops-195249},
  doi =		{10.4230/LIPIcs.OPODIS.2023.34},
  annote =	{Keywords: Data streams, Memory Management, Cache Policy, ML}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2020.50
Brief Announcement: Jiffy: A Fast, Memory Efficient, Wait-Free Multi-Producers Single-Consumer Queue

Authors: Dolev Adas and Roy Friedman

Published in: LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020)

Abstract
In applications such as sharded data processing systems, data flow programming and load sharing applications, multiple concurrent data producers are feeding requests into the same data consumer. This can be naturally realized through concurrent queues, where each consumer pulls its tasks from its dedicated queue. For scalability, wait-free queues are often preferred over lock based structures. The vast majority of wait-free queue implementations, and even lock-free ones, support the multi-producer multi-consumer model. Yet, this comes at a premium, since implementing wait-free multi-producer multi-consumer queues requires utilizing complex helper data structures. The latter increases the memory consumption of such queues and limits their performance and scalability. Additionally, many such designs employ (hardware) cache unfriendly memory access patterns. In this work we study the implementation of wait-free multi-producer single-consumer queues. Specifically, we propose Jiffy, an efficient memory frugal novel wait-free multi-producer single-consumer queue and formally prove its correctness. We then compare the performance and memory requirements of Jiffy with other state of the art lock-free and wait-free queues. We show that indeed Jiffy can maintain good performance with up to 128 threads, delivers better throughput than other constructions we compared against, and consumes less memory.
Cite as

Dolev Adas and Roy Friedman. Brief Announcement: Jiffy: A Fast, Memory Efficient, Wait-Free Multi-Producers Single-Consumer Queue. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 50:1-50:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{adas_et_al:LIPIcs.DISC.2020.50,
  author =	{Adas, Dolev and Friedman, Roy},
  title =	{{Brief Announcement: Jiffy: A Fast, Memory Efficient, Wait-Free Multi-Producers Single-Consumer Queue}},
  booktitle =	{34th International Symposium on Distributed Computing (DISC 2020)},
  pages =	{50:1--50:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-168-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{179},
  editor =	{Attiya, Hagit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.50},
  URN =		{urn:nbn:de:0030-drops-131287},
  doi =		{10.4230/LIPIcs.DISC.2020.50},
  annote =	{Keywords: Wait-freedom, MPSC Queues, Concurrent data-structures}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2019
LIPIcs, Vol. 153, OPODIS 2019, Complete Volume

Authors: Pascal Felber, Roy Friedman, Seth Gilbert, and Avery Miller

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
LIPIcs, Vol. 153, OPODIS 2019, Complete Volume
Cite as

23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 1-564, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@Proceedings{felber_et_al:LIPIcs.OPODIS.2019,
  title =	{{LIPIcs, Vol. 153, OPODIS 2019, Complete Volume}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{1--564},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019},
  URN =		{urn:nbn:de:0030-drops-119510},
  doi =		{10.4230/LIPIcs.OPODIS.2019},
  annote =	{Keywords: LIPIcs, Vol. 153, OPODIS 2019, Complete Volume}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2019.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Pascal Felber, Roy Friedman, Seth Gilbert, and Avery Miller

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

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

23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 0:i-0:xxii, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{felber_et_al:LIPIcs.OPODIS.2019.0,
  author =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{0:i--0:xxii},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.0},
  URN =		{urn:nbn:de:0030-drops-117869},
  doi =		{10.4230/LIPIcs.OPODIS.2019.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
Keynote Abstract
DOI: 10.4230/LIPIcs.OPODIS.2019.1
Demystifying Bitcoin (Keynote Abstract)

Authors: Rachid Guerraoui

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
This talk will explain the bitcoin algorithm from the distributed computing perspective, precisely define the underlying double-payment problem, and present a much simpler alternative to solve the problem without relying on consensus and consuming so much energy. Rachid Guerraoui is professor in Computer Science at EPFL where he leads the Distributed Computing Laboratory. He worked in the past with École des Mines de Paris, CEA Saclay, HP Labs in Palo Alto and MIT. He has been elected ACM Fellow and Professor of the College de France. He was awarded a Senior ERC Grant and a Google Focused Award.
Cite as

Rachid Guerraoui. Demystifying Bitcoin (Keynote Abstract). In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, p. 1:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{guerraoui:LIPIcs.OPODIS.2019.1,
  author =	{Guerraoui, Rachid},
  title =	{{Demystifying Bitcoin}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.1},
  URN =		{urn:nbn:de:0030-drops-117870},
  doi =		{10.4230/LIPIcs.OPODIS.2019.1},
  annote =	{Keywords: Bitcoin, Payment systems}
}
Document
Keynote Abstract
DOI: 10.4230/LIPIcs.OPODIS.2019.2
Distributed Optimization And Approximation: How Difficult Can It Be? (Keynote Abstract)

Authors: Keren Censor-Hillel

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
We know that exact distributed algorithms for optimization problems cannot be fast. To overcome these barriers, very efficient approximation algorithms have been designed in various distributed settings. But for very small approximation factors, a mystery remains: Why do we not have fast distributed algorithms for very small approximations factors in bandwidth restricted settings? This talk will overview the state-of-the-art of distributed optimization and approximation algorithms and discuss the major challenges in determining the complexity of small approximations.
Cite as

Keren Censor-Hillel. Distributed Optimization And Approximation: How Difficult Can It Be? (Keynote Abstract). In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{censorhillel:LIPIcs.OPODIS.2019.2,
  author =	{Censor-Hillel, Keren},
  title =	{{Distributed Optimization And Approximation: How Difficult Can It Be?}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.2},
  URN =		{urn:nbn:de:0030-drops-117886},
  doi =		{10.4230/LIPIcs.OPODIS.2019.2},
  annote =	{Keywords: Distributed graph algorithms, Optimization and approximations}
}
Document
Keynote Abstract
DOI: 10.4230/LIPIcs.OPODIS.2019.3
Snap ML - Accelerated Machine Learning for Big Data (Keynote Abstract)

Authors: Haris Pozidis

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
Snap Machine Learning (Snap ML) is a new software library for training popular machine learning models, characterized by very high performance, scalability to TB-scale datasets and high resource efficiency. It continuously evolves and currently supports generalized linear models, decision trees, random forests and gradient boosting machines. Snap ML has been built to address the needs of business applications, which often have to deal with high-volume data, react fast to changing environments, and use resources efficiently to drive down cost. The high efficiency of Snap ML, in particular in dealing with big data, comes from innovations in distributed optimization, among other things. This talk will review the principles of the Snap ML library, explain how it achieves high speed and scalability, and present several cases of business workloads that demonstrate the benefits offered by Snap ML. Haris Pozidis manages the Cloud Storage and Analytics group at IBM Research in Zurich, Switzerland. He was with Philips Research, Eindhoven, The Netherlands, before joining IBM. He has worked on read channel design for DVD and Blu-ray Disc at Philips, and played a key role in developing the first scanning probe-based data storage system at IBM, the “Millipede”. His current focus is on the development of Flash memory controllers for all-flash arrays, on phase change memory technology and system solutions, and on accelerated software libraries for machine learning. He holds over 120 US patents, has co-authored more than 120 publications, is an IBM Principal Research Scientist and Master Inventor, and a Senior Member of the IEEE.
Cite as

Haris Pozidis. Snap ML - Accelerated Machine Learning for Big Data (Keynote Abstract). In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, p. 3:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{pozidis:LIPIcs.OPODIS.2019.3,
  author =	{Pozidis, Haris},
  title =	{{Snap ML - Accelerated Machine Learning for Big Data}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{3:1--3:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.3},
  URN =		{urn:nbn:de:0030-drops-117899},
  doi =		{10.4230/LIPIcs.OPODIS.2019.3},
  annote =	{Keywords: Machine Learning, Big Data}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2019.4
FairLedger: A Fair Blockchain Protocol for Financial Institutions

Authors: Kfir Lev-Ari, Alexander Spiegelman, Idit Keidar, and Dahlia Malkhi

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
Financial institutions nowadays are looking into technologies for permissioned blockchains. A major effort in this direction is Hyperledger, an open source project hosted by the Linux Foundation and backed by a consortium of over a hundred companies. A key component in permissioned blockchain protocols is a byzantine fault tolerant (BFT) consensus engine that orders transactions. However, currently available BFT solutions in Hyperledger (as well as in the literature at large) are inadequate for financial settings; they are not designed to ensure fairness or to tolerate the selfish behavior that inevitably arises when financial institutions strive to maximize their own profit. We present FairLedger, a permissioned BFT blockchain protocol, which is fair, deigned to deal with rational behavior, and, no less important, easy to understand and implement. Our secret sauce is a new communication abstraction called detectable all-to-all (DA2A), which allows us to detect players (byzantine or rational) that deviate from the protocol and punish them. We implement FairLedger in the Hyperledger open source project using the Iroha framework - one of the biggest projects therein. To evaluate FairLegder’s performance, we also implement it in the PBFT framework and compare the two protocols. Our results show that in failure-free scenarios in wide-area settings, FairLedger achieves better throughput than both Iroha’s implementation and PBFT.
Cite as

Kfir Lev-Ari, Alexander Spiegelman, Idit Keidar, and Dahlia Malkhi. FairLedger: A Fair Blockchain Protocol for Financial Institutions. In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 4:1-4:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{levari_et_al:LIPIcs.OPODIS.2019.4,
  author =	{Lev-Ari, Kfir and Spiegelman, Alexander and Keidar, Idit and Malkhi, Dahlia},
  title =	{{FairLedger: A Fair Blockchain Protocol for Financial Institutions}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{4:1--4:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.4},
  URN =		{urn:nbn:de:0030-drops-117904},
  doi =		{10.4230/LIPIcs.OPODIS.2019.4},
  annote =	{Keywords: Blockchain, Fairness, Byzantine fault tolerance, Rational players, Equilibrium}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2019.5
Deconstructing Stellar Consensus

Authors: Álvaro García-Pérez and Maria A. Schett

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
Some of the recent blockchain proposals, such as Stellar and Ripple, allow for open membership while using quorum-like structures typical for classical Byzantine consensus with closed membership. This is achieved by constructing quorums in a decentralised way: each participant independently chooses whom to trust, and quorums arise from these individual decisions. Unfortunately, the consensus protocols underlying such blockchains are poorly understood, and their correctness has not been rigorously investigated. In this paper we rigorously prove correct the Stellar Consensus Protocol (SCP), with our proof giving insights into the protocol structure and its use of lower-level abstractions. To this end, we first propose an abstract version of SCP that uses as a black box Stellar’s federated voting primitive (analogous to reliable Byzantine broadcast), previously investigated by García-Pérez and Gotsman [Álvaro García-Pérez and Alexey Gotsman, 2018]. The abstract consensus protocol highlights a modular structure in Stellar and can be proved correct by reusing the previous results on federated voting. However, it is unsuited for realistic implementations, since its processes maintain infinite state. We thus establish a refinement between the abstract protocol and the concrete SCP that uses only finite state, thereby carrying over the result about the correctness of former to the latter. Our results help establish the theoretical foundations of decentralised blockchains like Stellar and gain confidence in their correctness.
Cite as

Álvaro García-Pérez and Maria A. Schett. Deconstructing Stellar Consensus. In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 5:1-5:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{garciaperez_et_al:LIPIcs.OPODIS.2019.5,
  author =	{Garc{\'\i}a-P\'{e}rez, \'{A}lvaro and Schett, Maria A.},
  title =	{{Deconstructing Stellar Consensus}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{5:1--5:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.5},
  URN =		{urn:nbn:de:0030-drops-117910},
  doi =		{10.4230/LIPIcs.OPODIS.2019.5},
  annote =	{Keywords: Blockchain, Consensus protocol, Stellar, Byzantine quorum systems}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2019.6
Byzantine-Tolerant Set-Constrained Delivery Broadcast

Authors: Alex Auvolat, Michel Raynal, and François Taïani

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
Set-Constrained Delivery Broadcast (SCD-broadcast), recently introduced at ICDCN 2018, is a high-level communication abstraction that captures ordering properties not between individual messages but between sets of messages. More precisely, it allows processes to broadcast messages and deliver sets of messages, under the constraint that if a process delivers a set containing a message m before a set containing a message m', then no other process delivers first a set containing m' and later a set containing m. It has been shown that SCD-broadcast and read/write registers are computationally equivalent, and an algorithm implementing SCD-broadcast is known in the context of asynchronous message passing systems prone to crash failures. This paper introduces a Byzantine-tolerant SCD-broadcast algorithm, which we call BSCD-broadcast. Our proposed algorithm assumes an underlying basic Byzantine-tolerant reliable broadcast abstraction. We first introduce an intermediary communication primitive, Byzantine FIFO broadcast (BFIFO-broadcast), which we then use as a primitive in our final BSCD-broadcast algorithm. Unlike the original SCD-broadcast algorithm that is tolerant to up to t<n/2 crashing processes, and unlike the underlying Byzantine reliable broadcast primitive that is tolerant to up to t<n/3 Byzantine processes, our BSCD-broadcast algorithm is tolerant to up to t<n/4 Byzantine processes. As an illustration of the high abstraction power provided by the BSCD-broadcast primitive, we show that it can be used to implement a Byzantine-tolerant read/write snapshot object in an extremely simple way.
Cite as

Alex Auvolat, Michel Raynal, and François Taïani. Byzantine-Tolerant Set-Constrained Delivery Broadcast. In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 6:1-6:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{auvolat_et_al:LIPIcs.OPODIS.2019.6,
  author =	{Auvolat, Alex and Raynal, Michel and Ta\"{i}ani, Fran\c{c}ois},
  title =	{{Byzantine-Tolerant Set-Constrained Delivery Broadcast}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{6:1--6:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.6},
  URN =		{urn:nbn:de:0030-drops-117922},
  doi =		{10.4230/LIPIcs.OPODIS.2019.6},
  annote =	{Keywords: Algorithm, Asynchronous system, Byzantine process, Communication abstraction, Distributed computing, Distributed software engineering, Fault-tolerance, Message-passing, Modularity, Read/write snapshot object, Reliable broadcast, Set-constrained message delivery}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2019.7
Asymmetric Distributed Trust

Authors: Christian Cachin and Björn Tackmann

Published in: LIPIcs, Volume 153, 23rd International Conference on Principles of Distributed Systems (OPODIS 2019)

Abstract
Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust assumptions. They can be found at the core of many algorithms for implementing reliable broadcasts, shared memory, consensus and other problems. This paper introduces asymmetric Byzantine quorum systems that model subjective trust. Every process is free to choose which combinations of other processes it trusts and which ones it considers faulty. Asymmetric quorum systems strictly generalize standard Byzantine quorum systems, which have only one global trust assumption for all processes. This work also presents protocols that implement abstractions of shared memory and broadcast primitives with processes prone to Byzantine faults and asymmetric trust. The model and protocols pave the way for realizing more elaborate algorithms with asymmetric trust.
Cite as

Christian Cachin and Björn Tackmann. Asymmetric Distributed Trust. In 23rd International Conference on Principles of Distributed Systems (OPODIS 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 153, pp. 7:1-7:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{cachin_et_al:LIPIcs.OPODIS.2019.7,
  author =	{Cachin, Christian and Tackmann, Bj\"{o}rn},
  title =	{{Asymmetric Distributed Trust}},
  booktitle =	{23rd International Conference on Principles of Distributed Systems (OPODIS 2019)},
  pages =	{7:1--7:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-133-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{153},
  editor =	{Felber, Pascal and Friedman, Roy and Gilbert, Seth and Miller, Avery},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2019.7},
  URN =		{urn:nbn:de:0030-drops-117933},
  doi =		{10.4230/LIPIcs.OPODIS.2019.7},
  annote =	{Keywords: Quorums, consensus, distributed trust, blockchains, cryptocurrencies}
}
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