62 Search Results for "Zabrocki,Mike"

Volume

Dagstuhl Follow-Ups, Volume 6

Artificial and Computational Intelligence in Games

Editors: Simon M. Lucas, Michael Mateas, Mike Preuss, Pieter Spronck, and Julian Togelius

Document
DOI: 10.4230/LIPIcs.AFT.2023.30
Time Is Money: Strategic Timing Games in Proof-Of-Stake Protocols

Authors: Caspar Schwarz-Schilling, Fahad Saleh, Thomas Thiery, Jennifer Pan, Nihar Shah, and Barnabé Monnot

Published in: LIPIcs, Volume 282, 5th Conference on Advances in Financial Technologies (AFT 2023)

Abstract
We propose a model suggesting that rational consensus participants may play timing games, and strategically delay their block proposal to optimize MEV capture, while still ensuring the proposal’s inclusion in the canonical chain. In this context, ensuring economic fairness among consensus participants is critical to preserving decentralization. We contend that a model grounded in rational consensus participation provides a more accurate portrayal of behavior in economically incentivized systems such as blockchain protocols. We empirically investigate timing games on the Ethereum network and demonstrate that while timing games are worth playing, they are not currently being exploited by consensus participants. By quantifying the marginal value of time, we uncover strong evidence pointing towards their future potential, despite the limited exploitation of MEV capture observed at present.
Cite as

Caspar Schwarz-Schilling, Fahad Saleh, Thomas Thiery, Jennifer Pan, Nihar Shah, and Barnabé Monnot. Time Is Money: Strategic Timing Games in Proof-Of-Stake Protocols. In 5th Conference on Advances in Financial Technologies (AFT 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 282, pp. 30:1-30:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{schwarzschilling_et_al:LIPIcs.AFT.2023.30,
  author =	{Schwarz-Schilling, Caspar and Saleh, Fahad and Thiery, Thomas and Pan, Jennifer and Shah, Nihar and Monnot, Barnab\'{e}},
  title =	{{Time Is Money: Strategic Timing Games in Proof-Of-Stake Protocols}},
  booktitle =	{5th Conference on Advances in Financial Technologies (AFT 2023)},
  pages =	{30:1--30:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-303-4},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{282},
  editor =	{Bonneau, Joseph and Weinberg, S. Matthew},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2023.30},
  URN =		{urn:nbn:de:0030-drops-192193},
  doi =		{10.4230/LIPIcs.AFT.2023.30},
  annote =	{Keywords: blockchain, proof-of-stake, game theory, maximal extractable value}
}
Document
Short Paper
DOI: 10.4230/LIPIcs.GIScience.2023.38
Exascale Agent-Based Modelling for Policy Evaluation in Real-Time (ExAMPLER) (Short Paper)

Authors: Alison Heppenstall, J. Gary Polhill, Mike Batty, Matt Hare, Doug Salt, and Richard Milton

Published in: LIPIcs, Volume 277, 12th International Conference on Geographic Information Science (GIScience 2023)

Abstract
Exascale computing can potentially revolutionise the way in which we design and build agent-based models (ABM) through, for example, enabling scaling up, as well as robust calibration and validation. At present, there is no exascale computing operating with ABM (that we are aware of), but pockets of work using High Performance Computing (HPC). While exascale computing is expected to become more widely available towards the latter half of this decade, the ABM community is largely unaware of the requirements for exascale computing for agent-based modelling to support policy evaluation. This project will engage with the ABM community to understand what computing resources are currently used, what we need (both in terms of hardware and software) and to set out a roadmap by which to make it happen.
Cite as

Alison Heppenstall, J. Gary Polhill, Mike Batty, Matt Hare, Doug Salt, and Richard Milton. Exascale Agent-Based Modelling for Policy Evaluation in Real-Time (ExAMPLER) (Short Paper). In 12th International Conference on Geographic Information Science (GIScience 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 277, pp. 38:1-38:5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{heppenstall_et_al:LIPIcs.GIScience.2023.38,
  author =	{Heppenstall, Alison and Polhill, J. Gary and Batty, Mike and Hare, Matt and Salt, Doug and Milton, Richard},
  title =	{{Exascale Agent-Based Modelling for Policy Evaluation in Real-Time (ExAMPLER)}},
  booktitle =	{12th International Conference on Geographic Information Science (GIScience 2023)},
  pages =	{38:1--38:5},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-288-4},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{277},
  editor =	{Beecham, Roger and Long, Jed A. and Smith, Dianna and Zhao, Qunshan and Wise, Sarah},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.GIScience.2023.38},
  URN =		{urn:nbn:de:0030-drops-189334},
  doi =		{10.4230/LIPIcs.GIScience.2023.38},
  annote =	{Keywords: Exascale computing, Agent-Based Modelling, Policy evaluation}
}
Document
DOI: 10.4230/OASIcs.Tokenomics.2022.6
Maximal Extractable Value (MEV) Protection on a DAG

Authors: Dahlia Malkhi and Pawel Szalachowski

Published in: OASIcs, Volume 110, 4th International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2022)

Abstract
Many cryptocurrency platforms are vulnerable to Maximal Extractable Value (MEV) attacks [Daian et al., 2020], where a malicious consensus leader can inject transactions or change the order of user transactions to maximize its profit. A promising line of research in MEV mitigation is to enhance the Byzantine fault tolerance (BFT) consensus core of blockchains by new functionalities, like hiding transaction contents, such that malicious parties cannot analyze and exploit them until they are ordered. An orthogonal line of research demonstrates excellent performance for BFT protocols designed around Directed Acyclic Graphs (DAG). They provide high throughput by keeping high network utilization, decoupling transactions' dissemination from their metadata ordering, and encoding consensus logic efficiently over a DAG representing a causal ordering of disseminated messages. This paper explains how to combine these two advances. It introduces a DAG-based protocol called Fino, that integrates MEV-resistance features into DAG-based BFT without delaying the steady spreading of transactions by the DAG transport and with zero message overhead. The scheme operates without complex secret share verifiability or recoverability, and avoids costly threshold encryption.
Cite as

Dahlia Malkhi and Pawel Szalachowski. Maximal Extractable Value (MEV) Protection on a DAG. In 4th International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2022). Open Access Series in Informatics (OASIcs), Volume 110, pp. 6:1-6:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{malkhi_et_al:OASIcs.Tokenomics.2022.6,
  author =	{Malkhi, Dahlia and Szalachowski, Pawel},
  title =	{{Maximal Extractable Value (MEV) Protection on a DAG}},
  booktitle =	{4th International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2022)},
  pages =	{6:1--6:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-274-7},
  ISSN =	{2190-6807},
  year =	{2023},
  volume =	{110},
  editor =	{Amoussou-Guenou, Yackolley and Kiayias, Aggelos and Verdier, Marianne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.Tokenomics.2022.6},
  URN =		{urn:nbn:de:0030-drops-184231},
  doi =		{10.4230/OASIcs.Tokenomics.2022.6},
  annote =	{Keywords: DAG, MEV, consensus, BFT}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.CONCUR.2022.2
Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions (Invited Talk)

Authors: Philippa Gardner

Published in: LIPIcs, Volume 243, 33rd International Conference on Concurrency Theory (CONCUR 2022)

Abstract
Scalable verification for concurrent programs with shared memory is a long-standing, difficult problem. In 2004, O'Hearn and Brookes introduced concurrent separation logic to provide compositional reasoning about coarse-grained concurrent programs with synchronisation primitives (Gödel prize, 2016). In 2010, I introduced logical abstraction (the fiction of separation) to CSL, developing the CAP logic for reasoning about fine-grained concurrent programs in general and fine-grained lock algorithms in particular. In one logic, it was possible to provide two-sided specifications of concurrent operations, with formally verified implementations and clients. In 2014, I introduced logical atomicity (the fiction of atomicity) to concurrent separation logics, developing the TaDA logic to capture when individual operations behave atomically. Unlike CAP, where synchronisation primitives leak into the specifications, with TaDA the specifications are "just right" in that they provide more general atomic functions specifications to capture, for example, the full behaviour of lock operations. In 2021, I introduced environment liveness conditions to concurrent separation logics, developing the TaDA Live logic for reasoning compositionally about the termination of blocking fine-grained concurrent programs. The crucial challenge is how to deal with abstract atomic blocking: that is, abstract atomic operations that have blocking behaviour arising from busy-waiting patterns as found in, for example, fine-grained spin locks. The fundamental innovation is with the design of abstract specifications that capture this blocking behaviour as liveness assumptions on the environment. In this talk, I will explain this on-going journey in the wonderful world of concurrent separation logics. I will also explain why I have a bright green office chair in the corner of my office, patterned in gold lamé. Many thanks to my fabulous coauthors on concurrent separation logics: Thomas Dinsdale-Young, Emanuele D'Osualdo, Mike Dodds, Azadeh Farzan, Matthew Parkinson, Pedro da Rocha Pinto, Julian Sutherland, Viktor Vafeiadis and more. Suggested Reading: - Peter O'Hearn: Resources, Concurrency and Local Reasoning, Journal of Theoretical Computer Science, Festschrift for John C Reynolds 70th birthday, 2007. - Thomas Dinsdale-Young, Pedro da Rocha Pinto and Philippa Gardner: A Perspective on Specifying and Verifying Concurrent Modules, Journal of Logical and Algebraic Methods in Programming, 2018. - Emanuele D'Osualdo, Azadeh Farzan, Philippa Gardner and Julian Sutherland: TaDA Live: Compositional Reasoning for Termination of Fine-grained Concurrent Programs, ACM Transactions on Programming Languages and Systems (TOPLAS), 2021.
Cite as

Philippa Gardner. Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions (Invited Talk). In 33rd International Conference on Concurrency Theory (CONCUR 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 243, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{gardner:LIPIcs.CONCUR.2022.2,
  author =	{Gardner, Philippa},
  title =	{{Concurrent Separation Logics: Logical Abstraction, Logical Atomicity and Environment Liveness Conditions}},
  booktitle =	{33rd International Conference on Concurrency Theory (CONCUR 2022)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-246-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{243},
  editor =	{Klin, Bartek and Lasota, S{\l}awomir and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2022.2},
  URN =		{urn:nbn:de:0030-drops-170659},
  doi =		{10.4230/LIPIcs.CONCUR.2022.2},
  annote =	{Keywords: Concurrent separation logic}
}
Document
DOI: 10.4230/LIPIcs.STACS.2022.14
On Explicit Constructions of Extremely Depth Robust Graphs

Authors: Jeremiah Blocki, Mike Cinkoske, Seunghoon Lee, and Jin Young Son

Published in: LIPIcs, Volume 219, 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)

Abstract
A directed acyclic graph G = (V,E) is said to be (e,d)-depth robust if for every subset S ⊆ V of |S| ≤ e nodes the graph G-S still contains a directed path of length d. If the graph is (e,d)-depth-robust for any e,d such that e+d ≤ (1-ε)|V| then the graph is said to be ε-extreme depth-robust. In the field of cryptography, (extremely) depth-robust graphs with low indegree have found numerous applications including the design of side-channel resistant Memory-Hard Functions, Proofs of Space and Replication and in the design of Computationally Relaxed Locally Correctable Codes. In these applications, it is desirable to ensure the graphs are locally navigable, i.e., there is an efficient algorithm GetParents running in time polylog|V| which takes as input a node v ∈ V and returns the set of v’s parents. We give the first explicit construction of locally navigable ε-extreme depth-robust graphs with indegree O(log |V|). Previous constructions of ε-extreme depth-robust graphs either had indegree ω̃(log² |V|) or were not explicit.
Cite as

Jeremiah Blocki, Mike Cinkoske, Seunghoon Lee, and Jin Young Son. On Explicit Constructions of Extremely Depth Robust Graphs. In 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 219, pp. 14:1-14:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{blocki_et_al:LIPIcs.STACS.2022.14,
  author =	{Blocki, Jeremiah and Cinkoske, Mike and Lee, Seunghoon and Son, Jin Young},
  title =	{{On Explicit Constructions of Extremely Depth Robust Graphs}},
  booktitle =	{39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)},
  pages =	{14:1--14:11},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-222-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{219},
  editor =	{Berenbrink, Petra and Monmege, Benjamin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2022.14},
  URN =		{urn:nbn:de:0030-drops-158241},
  doi =		{10.4230/LIPIcs.STACS.2022.14},
  annote =	{Keywords: Depth-Robust Graphs, Explicit Constructions, Data-Independent Memory Hard Functions, Proofs of Space and Replication}
}
Document
DOI: 10.4230/LIPIcs.STACS.2022.55
Superlinear Lower Bounds Based on ETH

Authors: András Z. Salamon and Michael Wehar

Published in: LIPIcs, Volume 219, 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)

Abstract
We introduce techniques for proving superlinear conditional lower bounds for polynomial time problems. In particular, we show that CircuitSAT for circuits with m gates and log(m) inputs (denoted by log-CircuitSAT) is not decidable in essentially-linear time unless the exponential time hypothesis (ETH) is false and k-Clique is decidable in essentially-linear time in terms of the graph’s size for all fixed k. Such conditional lower bounds have previously only been demonstrated relative to the strong exponential time hypothesis (SETH). Our results therefore offer significant progress towards proving unconditional superlinear time complexity lower bounds for natural problems in polynomial time.
Cite as

András Z. Salamon and Michael Wehar. Superlinear Lower Bounds Based on ETH. In 39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 219, pp. 55:1-55:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{salamon_et_al:LIPIcs.STACS.2022.55,
  author =	{Salamon, Andr\'{a}s Z. and Wehar, Michael},
  title =	{{Superlinear Lower Bounds Based on ETH}},
  booktitle =	{39th International Symposium on Theoretical Aspects of Computer Science (STACS 2022)},
  pages =	{55:1--55:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-222-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{219},
  editor =	{Berenbrink, Petra and Monmege, Benjamin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2022.55},
  URN =		{urn:nbn:de:0030-drops-158652},
  doi =		{10.4230/LIPIcs.STACS.2022.55},
  annote =	{Keywords: Circuit Satisfiability, Conditional Lower Bounds, Exponential Time Hypothesis, Limited Nondeterminism}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2021.20
The Open Algebraic Path Problem

Authors: Jade Master

Published in: LIPIcs, Volume 211, 9th Conference on Algebra and Coalgebra in Computer Science (CALCO 2021)

Abstract
The algebraic path problem provides a general setting for shortest path algorithms in optimization and computer science. We explain the universal property of solutions to the algebraic path problem by constructing a left adjoint functor whose values are given by these solutions. This paper extends the algebraic path problem to networks equipped with input and output boundaries. We show that the algebraic path problem is functorial as a mapping from a double category whose horizontal composition is gluing of open networks. We introduce functional open matrices, for which the functoriality of the algebraic path problem has a more practical expression.
Cite as

Jade Master. The Open Algebraic Path Problem. In 9th Conference on Algebra and Coalgebra in Computer Science (CALCO 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 211, pp. 20:1-20:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{master:LIPIcs.CALCO.2021.20,
  author =	{Master, Jade},
  title =	{{The Open Algebraic Path Problem}},
  booktitle =	{9th Conference on Algebra and Coalgebra in Computer Science (CALCO 2021)},
  pages =	{20:1--20:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-212-9},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{211},
  editor =	{Gadducci, Fabio and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2021.20},
  URN =		{urn:nbn:de:0030-drops-153754},
  doi =		{10.4230/LIPIcs.CALCO.2021.20},
  annote =	{Keywords: The Algebraic Path Problem, Open Systems, Shortest Paths, Categorical Semantics, Compositionality}
}
Document
DOI: 10.4230/LIPIcs.ESA.2021.39
Data Structures Lower Bounds and Popular Conjectures

Authors: Pavel Dvořák, Michal Koucký, Karel Král, and Veronika Slívová

Published in: LIPIcs, Volume 204, 29th Annual European Symposium on Algorithms (ESA 2021)

Abstract
In this paper, we investigate the relative power of several conjectures that attracted recently lot of interest. We establish a connection between the Network Coding Conjecture (NCC) of Li and Li [Li and Li, 2004] and several data structure problems such as non-adaptive function inversion of Hellman [M. Hellman, 1980] and the well-studied problem of polynomial evaluation and interpolation. In turn these data structure problems imply super-linear circuit lower bounds for explicit functions such as integer sorting and multi-point polynomial evaluation.
Cite as

Pavel Dvořák, Michal Koucký, Karel Král, and Veronika Slívová. Data Structures Lower Bounds and Popular Conjectures. In 29th Annual European Symposium on Algorithms (ESA 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 204, pp. 39:1-39:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{dvorak_et_al:LIPIcs.ESA.2021.39,
  author =	{Dvo\v{r}\'{a}k, Pavel and Kouck\'{y}, Michal and Kr\'{a}l, Karel and Sl{\'\i}vov\'{a}, Veronika},
  title =	{{Data Structures Lower Bounds and Popular Conjectures}},
  booktitle =	{29th Annual European Symposium on Algorithms (ESA 2021)},
  pages =	{39:1--39:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-204-4},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{204},
  editor =	{Mutzel, Petra and Pagh, Rasmus and Herman, Grzegorz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2021.39},
  URN =		{urn:nbn:de:0030-drops-146207},
  doi =		{10.4230/LIPIcs.ESA.2021.39},
  annote =	{Keywords: Data structures, Circuits, Lower bounds, Network Coding Conjecture}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2021.58
Haystack Hunting Hints and Locker Room Communication

Authors: Artur Czumaj, George Kontogeorgiou, and Mike Paterson

Published in: LIPIcs, Volume 198, 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)

Abstract
We want to efficiently find a specific object in a large unstructured set, which we model by a random n-permutation, and we have to do it by revealing just a single element. Clearly, without any help this task is hopeless and the best one can do is to select the element at random, and achieve the success probability 1/n. Can we do better with some small amount of advice about the permutation, even without knowing the object sought? We show that by providing advice of just one integer in {0,1,… ,n-1}, one can improve the success probability considerably, by a Θ((log n)/(log log n)) factor. We study this and related problems, and show asymptotically matching upper and lower bounds for their optimal probability of success. Our analysis relies on a close relationship of such problems to some intrinsic properties of random permutations related to the rencontres number.
Cite as

Artur Czumaj, George Kontogeorgiou, and Mike Paterson. Haystack Hunting Hints and Locker Room Communication. In 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 198, pp. 58:1-58:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{czumaj_et_al:LIPIcs.ICALP.2021.58,
  author =	{Czumaj, Artur and Kontogeorgiou, George and Paterson, Mike},
  title =	{{Haystack Hunting Hints and Locker Room Communication}},
  booktitle =	{48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)},
  pages =	{58:1--58:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-195-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{198},
  editor =	{Bansal, Nikhil and Merelli, Emanuela and Worrell, James},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2021.58},
  URN =		{urn:nbn:de:0030-drops-141270},
  doi =		{10.4230/LIPIcs.ICALP.2021.58},
  annote =	{Keywords: Random permutations, Search, Communication complexity}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2021.88
Sorting Short Integers

Authors: Michal Koucký and Karel Král

Published in: LIPIcs, Volume 198, 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)

Abstract
We build boolean circuits of size 𝒪(nm²) and depth 𝒪(log(n) + m log(m)) for sorting n integers each of m-bits. We build also circuits that sort n integers each of m-bits according to their first k bits that are of size 𝒪(nmk (1 + log^*(n) - log^*(m))) and depth 𝒪(log³(n)). This improves on the results of Asharov et al. [Asharov et al., 2021] and resolves some of their open questions.
Cite as

Michal Koucký and Karel Král. Sorting Short Integers. In 48th International Colloquium on Automata, Languages, and Programming (ICALP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 198, pp. 88:1-88:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{koucky_et_al:LIPIcs.ICALP.2021.88,
  author =	{Kouck\'{y}, Michal and Kr\'{a}l, Karel},
  title =	{{Sorting Short Integers}},
  booktitle =	{48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)},
  pages =	{88:1--88:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-195-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{198},
  editor =	{Bansal, Nikhil and Merelli, Emanuela and Worrell, James},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2021.88},
  URN =		{urn:nbn:de:0030-drops-141577},
  doi =		{10.4230/LIPIcs.ICALP.2021.88},
  annote =	{Keywords: sorting, small integers, boolean circuits}
}
Document
Invited Paper
DOI: 10.4230/LIPIcs.ITP.2021.1
The CakeML Project’s Quest for Ever Stronger Correctness Theorems (Invited Paper)

Authors: Magnus O. Myreen

Published in: LIPIcs, Volume 193, 12th International Conference on Interactive Theorem Proving (ITP 2021)

Abstract
The CakeML project has developed a proof-producing code generation mechanism for the HOL4 theorem prover, a verified compiler for ML and, using these, a number of verified application programs that are proved correct down to the machine code that runs them (in some cases, even down to the underlying hardware). The purpose of this extended abstract is to tell the story of the project and to point curious readers to publications where they can read more about specific contributions.
Cite as

Magnus O. Myreen. The CakeML Project’s Quest for Ever Stronger Correctness Theorems (Invited Paper). In 12th International Conference on Interactive Theorem Proving (ITP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 193, pp. 1:1-1:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{myreen:LIPIcs.ITP.2021.1,
  author =	{Myreen, Magnus O.},
  title =	{{The CakeML Project’s Quest for Ever Stronger Correctness Theorems}},
  booktitle =	{12th International Conference on Interactive Theorem Proving (ITP 2021)},
  pages =	{1:1--1:10},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-188-7},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{193},
  editor =	{Cohen, Liron and Kaliszyk, Cezary},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2021.1},
  URN =		{urn:nbn:de:0030-drops-138963},
  doi =		{10.4230/LIPIcs.ITP.2021.1},
  annote =	{Keywords: Program verification, interactive theorem proving}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2021.64
A New Connection Between Node and Edge Depth Robust Graphs

Authors: Jeremiah Blocki and Mike Cinkoske

Published in: LIPIcs, Volume 185, 12th Innovations in Theoretical Computer Science Conference (ITCS 2021)

Abstract
Given a directed acyclic graph (DAG) G = (V,E), we say that G is (e,d)-depth-robust (resp. (e,d)-edge-depth-robust) if for any set S ⊂ V (resp. S ⊆ E) of at most |S| ≤ e nodes (resp. edges) the graph G-S contains a directed path of length d. While edge-depth-robust graphs are potentially easier to construct many applications in cryptography require node depth-robust graphs with small indegree. We create a graph reduction that transforms an (e, d)-edge-depth-robust graph with m edges into a (e/2,d)-depth-robust graph with O(m) nodes and constant indegree. One immediate consequence of this result is the first construction of a provably ((n log log n)/log n, n/{(log n)^{1 + log log n}})-depth-robust graph with constant indegree, where previous constructions for e = (n log log n)/log n had d = O(n^{1-ε}). Our reduction crucially relies on ST-Robust graphs, a new graph property we introduce which may be of independent interest. We say that a directed, acyclic graph with n inputs and n outputs is (k₁, k₂)-ST-Robust if we can remove any k₁ nodes and there exists a subgraph containing at least k₂ inputs and k₂ outputs such that each of the k₂ inputs is connected to all of the k₂ outputs. If the graph if (k₁,n-k₁)-ST-Robust for all k₁ ≤ n we say that the graph is maximally ST-robust. We show how to construct maximally ST-robust graphs with constant indegree and O(n) nodes. Given a family 𝕄 of ST-robust graphs and an arbitrary (e, d)-edge-depth-robust graph G we construct a new constant-indegree graph Reduce(G, 𝕄) by replacing each node in G with an ST-robust graph from 𝕄. We also show that ST-robust graphs can be used to construct (tight) proofs-of-space and (asymptotically) improved wide-block labeling functions.
Cite as

Jeremiah Blocki and Mike Cinkoske. A New Connection Between Node and Edge Depth Robust Graphs. In 12th Innovations in Theoretical Computer Science Conference (ITCS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 185, pp. 64:1-64:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{blocki_et_al:LIPIcs.ITCS.2021.64,
  author =	{Blocki, Jeremiah and Cinkoske, Mike},
  title =	{{A New Connection Between Node and Edge Depth Robust Graphs}},
  booktitle =	{12th Innovations in Theoretical Computer Science Conference (ITCS 2021)},
  pages =	{64:1--64:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-177-1},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{185},
  editor =	{Lee, James R.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2021.64},
  URN =		{urn:nbn:de:0030-drops-136038},
  doi =		{10.4230/LIPIcs.ITCS.2021.64},
  annote =	{Keywords: Depth robust graphs, memory hard functions}
}
Document
DOI: 10.4230/OASIcs.FMBC.2020.9
On the Formal Verification of the Stellar Consensus Protocol

Authors: Giuliano Losa and Mike Dodds

Published in: OASIcs, Volume 84, 2nd Workshop on Formal Methods for Blockchains (FMBC 2020)

Abstract
The Stellar Consensus Protocol (SCP) is a quorum-based BFT consensus protocol. However, instead of using threshold-based quorums, SCP is permissionless and its quorum system emerges from participants’ self-declared trust relationships. In this paper, we describe the methodology we deploy to formally verify the safety and liveness of SCP for arbitrary but fixed configurations. The proof uses a combination of Ivy and Isabelle/HOL. In Ivy, we model SCP in first-order logic, and we verify safety and liveness under eventual synchrony. In Isabelle/HOL, we prove the validity of our first-order encoding with respect to a more direct higher-order model. SCP is currently deployed in the Stellar Network, and we believe this is the first mechanized proof of both safety and liveness, specified in LTL, for a deployed BFT protocol.
Cite as

Giuliano Losa and Mike Dodds. On the Formal Verification of the Stellar Consensus Protocol. In 2nd Workshop on Formal Methods for Blockchains (FMBC 2020). Open Access Series in Informatics (OASIcs), Volume 84, pp. 9:1-9:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{losa_et_al:OASIcs.FMBC.2020.9,
  author =	{Losa, Giuliano and Dodds, Mike},
  title =	{{On the Formal Verification of the Stellar Consensus Protocol}},
  booktitle =	{2nd Workshop on Formal Methods for Blockchains (FMBC 2020)},
  pages =	{9:1--9:9},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-169-6},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{84},
  editor =	{Bernardo, Bruno and Marmsoler, Diego},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2020.9},
  URN =		{urn:nbn:de:0030-drops-134226},
  doi =		{10.4230/OASIcs.FMBC.2020.9},
  annote =	{Keywords: Consensus, Blockchains, First-Order Logic, Stellar, Ivy Prover, Decidability}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2020.2
On the Multi-Kind BahnCard Problem

Authors: Mike Timm and Sabine Storandt

Published in: OASIcs, Volume 85, 20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020)

Abstract
The BahnCard problem is an important problem in the realm of online decision making. In its original form, there is one kind of BahnCard associated with a certain price, which upon purchase reduces the ticket price of train journeys for a certain factor over a certain period of time. The problem consists of deciding on which dates BahnCards should be purchased such that the overall cost, that is, BahnCard prices plus (reduced) ticket prices, is minimized without having knowledge about the number and prices of future journeys. In this paper, we extend the problem such that multiple kinds of BahnCards are available for purchase. We provide an optimal offline algorithm, as well as online strategies with provable competitiveness factors. Furthermore, we describe and implement several heuristic online strategies and compare their competitiveness in realistic scenarios.
Cite as

Mike Timm and Sabine Storandt. On the Multi-Kind BahnCard Problem. In 20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020). Open Access Series in Informatics (OASIcs), Volume 85, pp. 2:1-2:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{timm_et_al:OASIcs.ATMOS.2020.2,
  author =	{Timm, Mike and Storandt, Sabine},
  title =	{{On the Multi-Kind BahnCard Problem}},
  booktitle =	{20th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2020)},
  pages =	{2:1--2:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-170-2},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{85},
  editor =	{Huisman, Dennis and Zaroliagis, Christos D.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2020.2},
  URN =		{urn:nbn:de:0030-drops-131382},
  doi =		{10.4230/OASIcs.ATMOS.2020.2},
  annote =	{Keywords: offline solution, competitiveness, traveller profiles}
}
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