5 Search Results for "Derka, Martin"

Document
DOI: 10.4230/LIPIcs.OPODIS.2025.27
Where to Place Your TEE? In Search of a Censorship-Resilient Design for Rollup Sequencers

Authors: Andrei Arusoaie, Claudiu-Nicu Bărbieru, Oana-Otilia Captarencu, Pascal Felber, Corentin Libert, Emanuel Onica, Etienne Rivière, Valerio Schiavoni, and Peterson Yuhala

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

Abstract
Ethereum is the dominant blockchain ecosystem capable of executing Turing-complete smart contracts. Rollups gained significant traction as the primary layer 2 (L2) solution meant to bring horizontal scalability to the main Ethereum network (L1). A core component of any rollup is the sequencer, which creates new L2 blocks to be submitted in rollup batches to L1. In most of the current rollup architectures, this component is centralised. As a result, these designs are prone to inconspicuous censorship practices by the sequencer. Trusted execution environments (TEEs) can guarantee the integrity of various sequencer components, which is instrumental in addressing censorship. However, the reaction of the system design to censorship attempts depends on where a TEE is integrated and which components it protects. In particular, this reaction is limited in the case of a monolithic TEE-protected sequencer design. Proposer-Builder Separation (PBS) is a non-monolithic paradigm adopted on L1, which separates the production of blocks from proposing them for inclusion in the blockchain. Recently, PBS has been considered for integration with L2 sequencers, with an impact on alleviating censorship. In this paper, we explore the design space of TEE-integrating PBS and non-PBS sequencer variants. First, we introduce a formal framework for the censorship actions that captures the specificity of the L2 sequencer. Then, we analyse to what extent the different designs address these censorship actions. Our main contribution is a novel design variation that allows for a precise observation of censored transactions. In the presence of TEEs, in a PBS setting, we demonstrate this precise observability, which is necessary to enable resilience to censorship.
Cite as

Andrei Arusoaie, Claudiu-Nicu Bărbieru, Oana-Otilia Captarencu, Pascal Felber, Corentin Libert, Emanuel Onica, Etienne Rivière, Valerio Schiavoni, and Peterson Yuhala. Where to Place Your TEE? In Search of a Censorship-Resilient Design for Rollup Sequencers. In 29th International Conference on Principles of Distributed Systems (OPODIS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 361, pp. 27:1-27:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{arusoaie_et_al:LIPIcs.OPODIS.2025.27,
  author =	{Arusoaie, Andrei and B\u{a}rbieru, Claudiu-Nicu and Captarencu, Oana-Otilia and Felber, Pascal and Libert, Corentin and Onica, Emanuel and Rivi\`{e}re, Etienne and Schiavoni, Valerio and Yuhala, Peterson},
  title =	{{Where to Place Your TEE? In Search of a Censorship-Resilient Design for Rollup Sequencers}},
  booktitle =	{29th International Conference on Principles of Distributed Systems (OPODIS 2025)},
  pages =	{27:1--27:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-409-3},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{361},
  editor =	{Arusoaie, Andrei and Onica, Emanuel and Spear, Michael and Tucci-Piergiovanni, Sara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2025.27},
  URN =		{urn:nbn:de:0030-drops-252000},
  doi =		{10.4230/LIPIcs.OPODIS.2025.27},
  annote =	{Keywords: Rollups, Trusted Execution Environments, Censorship}
}
Document
DOI: 10.4230/OASIcs.FMBC.2025.8
Formal Verification of a Fail-Safe Cross-Chain Bridge

Authors: Filip Marić, Bernhard Scholz, and Pavle Subotić

Published in: OASIcs, Volume 129, 6th International Workshop on Formal Methods for Blockchains (FMBC 2025)

Abstract
Cross-chain bridges are financial services that interconnect blockchains. High monetary values flow through these bridges, and their security must be safeguarded. However, designing real-world cross-chain bridges is a difficult endeavor. Due to blockchain’s closed-world nature, tokens cannot be transferred from a sender to a receiver chain; on the contrary, they need complex logic that maintains an equilibrium on both chains, even if either the chains or the bridge fail. This paper formally verifies a model of a novel fail-safe cross-chain bridge to ensure correctness. We define formal requirements and prove the bridge is safe using the Isabelle/HOL proof assistant.
Cite as

Filip Marić, Bernhard Scholz, and Pavle Subotić. Formal Verification of a Fail-Safe Cross-Chain Bridge. In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 8:1-8:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{maric_et_al:OASIcs.FMBC.2025.8,
  author =	{Mari\'{c}, Filip and Scholz, Bernhard and Suboti\'{c}, Pavle},
  title =	{{Formal Verification of a Fail-Safe Cross-Chain Bridge}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{8:1--8:18},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-371-3},
  ISSN =	{2190-6807},
  year =	{2025},
  volume =	{129},
  editor =	{Marmsoler, Diego and Xu, Meng},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FMBC.2025.8},
  URN =		{urn:nbn:de:0030-drops-230342},
  doi =		{10.4230/OASIcs.FMBC.2025.8},
  annote =	{Keywords: Cross-Chain Bridge, Formal Verification, Logic, Security}
}
Document
DOI: 10.4230/LIPIcs.SWAT.2018.10
On the Size of Outer-String Representations

Authors: Therese Biedl, Ahmad Biniaz, and Martin Derka

Published in: LIPIcs, Volume 101, 16th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2018)

Abstract
Outer-string graphs, i.e., graphs that can be represented as intersection of curves in 2D, all of which end in the outer-face, have recently received much interest, especially since it was shown that the independent set problem can be solved efficiently in such graphs. However, the run-time for the independent set problem depends on N, the number of segments in an outer-string representation, rather than the number n of vertices of the graph. In this paper, we argue that for some outer-string graphs, N must be exponential in n. We also study some special string graphs, viz. monotone string graphs, and argue that for them N can be assumed to be polynomial in n. Finally we give an algorithm for independent set in so-called strip-grounded monotone outer-string graphs that is polynomial in n.
Cite as

Therese Biedl, Ahmad Biniaz, and Martin Derka. On the Size of Outer-String Representations. In 16th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 101, pp. 10:1-10:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{biedl_et_al:LIPIcs.SWAT.2018.10,
  author =	{Biedl, Therese and Biniaz, Ahmad and Derka, Martin},
  title =	{{On the Size of Outer-String Representations}},
  booktitle =	{16th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2018)},
  pages =	{10:1--10:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-068-2},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{101},
  editor =	{Eppstein, David},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SWAT.2018.10},
  URN =		{urn:nbn:de:0030-drops-88360},
  doi =		{10.4230/LIPIcs.SWAT.2018.10},
  annote =	{Keywords: string graph, outer-string graph, size of representation, independent set}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2017.13
Crossing Number for Graphs with Bounded~Pathwidth

Authors: Therese Biedl, Markus Chimani, Martin Derka, and Petra Mutzel

Published in: LIPIcs, Volume 92, 28th International Symposium on Algorithms and Computation (ISAAC 2017)

Abstract
The crossing number is the smallest number of pairwise edge crossings when drawing a graph into the plane. There are only very few graph classes for which the exact crossing number is known or for which there at least exist constant approximation ratios. Furthermore, up to now, general crossing number computations have never been successfully tackled using bounded width of graph decompositions, like treewidth or pathwidth. In this paper, we for the first time show that crossing number is tractable (even in linear time) for maximal graphs of bounded pathwidth 3. The technique also shows that the crossing number and the rectilinear (a.k.a. straight-line) crossing number are identical for this graph class, and that we require only an O(n)xO(n)-grid to achieve such a drawing. Our techniques can further be extended to devise a 2-approximation for general graphs with pathwidth 3, and a 4w^3-approximation for maximal graphs of pathwidth w. This is a constant approximation for bounded pathwidth graphs.
Cite as

Therese Biedl, Markus Chimani, Martin Derka, and Petra Mutzel. Crossing Number for Graphs with Bounded~Pathwidth. In 28th International Symposium on Algorithms and Computation (ISAAC 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 92, pp. 13:1-13:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{biedl_et_al:LIPIcs.ISAAC.2017.13,
  author =	{Biedl, Therese and Chimani, Markus and Derka, Martin and Mutzel, Petra},
  title =	{{Crossing Number for Graphs with Bounded\textasciitildePathwidth}},
  booktitle =	{28th International Symposium on Algorithms and Computation (ISAAC 2017)},
  pages =	{13:1--13:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-054-5},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{92},
  editor =	{Okamoto, Yoshio and Tokuyama, Takeshi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2017.13},
  URN =		{urn:nbn:de:0030-drops-82570},
  doi =		{10.4230/LIPIcs.ISAAC.2017.13},
  annote =	{Keywords: Crossing Number, Graphs with Bounded Pathwidth}
}
Document
DOI: 10.4230/LIPIcs.SOCG.2015.141
1-String B_2-VPG Representation of Planar Graphs

Authors: Therese Biedl and Martin Derka

Published in: LIPIcs, Volume 34, 31st International Symposium on Computational Geometry (SoCG 2015)

Abstract
In this paper, we prove that every planar graph has a 1-string B_2-VPG representation - a string representation using paths in a rectangular grid that contain at most two bends. Furthermore, two paths representing vertices u, v intersect precisely once whenever there is an edge between u and v.
Cite as

Therese Biedl and Martin Derka. 1-String B_2-VPG Representation of Planar Graphs. In 31st International Symposium on Computational Geometry (SoCG 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 34, pp. 141-155, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{biedl_et_al:LIPIcs.SOCG.2015.141,
  author =	{Biedl, Therese and Derka, Martin},
  title =	{{1-String B\underline2-VPG Representation of Planar Graphs}},
  booktitle =	{31st International Symposium on Computational Geometry (SoCG 2015)},
  pages =	{141--155},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-83-5},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{34},
  editor =	{Arge, Lars and Pach, J\'{a}nos},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SOCG.2015.141},
  URN =		{urn:nbn:de:0030-drops-51323},
  doi =		{10.4230/LIPIcs.SOCG.2015.141},
  annote =	{Keywords: Graph drawing, string graphs, VPG graphs, planar graphs}
}
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