13 Search Results for "Weippl, Edgar"

Document
DOI: 10.4230/LIPIcs.ITCS.2026.19
Limitations to Computing Quadratic Functions on Reed-Solomon Encoded Data

Authors: Keller Blackwell and Mary Wootters

Published in: LIPIcs, Volume 362, 17th Innovations in Theoretical Computer Science Conference (ITCS 2026)

Abstract
We study the problem of low-bandwidth non-linear computation on Reed-Solomon encoded data. Given an [n,k] Reed-Solomon encoding of a message vector 𝐟 ∈ 𝔽_q^k, and a polynomial g ∈ 𝔽_q[X₁, X₂, …, X_k], a user wishing to evaluate g(𝐟) is given local query access to each codeword symbol. The query response is allowed to be the output of an arbitrary function evaluated locally on the codeword symbol, and the user’s aim is to minimize the total information downloaded in order to compute g(𝐟). This problem has been studied before for linear functions g; in this work we initiate the study of non-linear functions by starting with quadratic monomials. For q = p^e and distinct i,j ∈ [k], we show that any scheme evaluating the quadratic monomial g_{i,j} := X_i X_j must download at least 2 log₂(q-1) - 3 bits of information when p is an odd prime, and at least 2log₂(q-2) -4 bits when p = 2. When k = 2, our result shows that one cannot do significantly better than the naive bound of k log₂(q) bits, which is enough to recover all of 𝐟. This contrasts sharply with prior work for low-bandwidth evaluation of linear functions g(𝐟) over Reed-Solomon encoded data, for which it is possible to substantially improve upon this bound [Venkatesan Guruswami and Mary Wootters, 2016; Tamo et al., 2018; Shutty and Wootters, 2021; Kiah et al., 2024; Con and Tamo, 2022]. Some proofs have been omitted from this extended abstract; the full version can be found at [Keller Blackwell and Mary Wootters, 2025].
Cite as

Keller Blackwell and Mary Wootters. Limitations to Computing Quadratic Functions on Reed-Solomon Encoded Data. In 17th Innovations in Theoretical Computer Science Conference (ITCS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 362, pp. 19:1-19:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{blackwell_et_al:LIPIcs.ITCS.2026.19,
  author =	{Blackwell, Keller and Wootters, Mary},
  title =	{{Limitations to Computing Quadratic Functions on Reed-Solomon Encoded Data}},
  booktitle =	{17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
  pages =	{19:1--19:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-410-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{362},
  editor =	{Saraf, Shubhangi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.19},
  URN =		{urn:nbn:de:0030-drops-253064},
  doi =		{10.4230/LIPIcs.ITCS.2026.19},
  annote =	{Keywords: Distributed computation, Reed-Solomon codes}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2026.71
Lower Bounds on FSS from Dynamic Data Structures

Authors: Niv Gilboa and Daniel Weber

Published in: LIPIcs, Volume 362, 17th Innovations in Theoretical Computer Science Conference (ITCS 2026)

Abstract
In Function Secret Sharing (FSS), a dealer with a given function f: {0,1}ⁿ → 𝔾 from n bits to a commutative group 𝔾 such that f is in a function class ℱ shares succinct keys with two properties. Evaluating each key separately on a common input x results in additive shares of f(x) and any subset of the keys does not provide information on f. Two-party FSS schemes which are reducible to One-way Functions (OWF) have applications in cryptography, complexity, and in practical data security systems. We establish a two-way transformation between a two-party FSS scheme for a function class ℱ, which is black-box reducible to an OWF, or even black-box reducible to a family of Pseudo-Random Functions (PRF) and a dynamic data structure that supports range queries on ℱ. A data structure of this type enables dynamically adding functions to a multiset of functions F ⊆ ℱ, and answering range queries on the output of F, i.e., returning ∑_{f ∈ F} f(x) for a query x. The data structures are defined in one of several models which abstract RAM. The correspondence together with known lower bounds on the update time and the query time in data structures leads to the first non-trivial lower bounds on FSS schemes which are black-box reducible to PRF. These lower bounds apply to FSS schemes with polynomial key size and include: - For ℱ^d_{box}, the class of all functions which assign a constant group element β ∈ 𝔾 to any input in a specified d-dimensional box and 0 to all other inputs: if the key sharing function, Gen, runs in time polynomial in n and the evaluation function is Eval then: - If d ≥ 2 and 𝔾 = ℤ₂ then Eval’s running time is Ω ((n^{3/2})/(log³ n)). - If d ≥ 2 and 𝔾 is cyclic such that log |𝔾| = (1 + ε) n then Eval’s running time is Ω ((n/(log n)) ²). - If d > 2 is a constant and further, Gen and Eval correspond to operations on data structures in the Oblivious Group Model (this includes all known FSS from OWF techniques), then the product of Eval’s time and the key size is Ω(n^{d-1}). - For ℱ_{mono}, the class of all monomials ax^b ∈ 𝔽_{2ⁿ}[X] such that b ≤ B, assuming n^{ω(1)} ≤ B ≤ 2^{n/4}: if Gen runs in polynomial time, then Eval’s running time is Ω ((n √{log B})/(log² n)).
Cite as

Niv Gilboa and Daniel Weber. Lower Bounds on FSS from Dynamic Data Structures. In 17th Innovations in Theoretical Computer Science Conference (ITCS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 362, pp. 71:1-71:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{gilboa_et_al:LIPIcs.ITCS.2026.71,
  author =	{Gilboa, Niv and Weber, Daniel},
  title =	{{Lower Bounds on FSS from Dynamic Data Structures}},
  booktitle =	{17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
  pages =	{71:1--71:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-410-9},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{362},
  editor =	{Saraf, Shubhangi},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.71},
  URN =		{urn:nbn:de:0030-drops-253585},
  doi =		{10.4230/LIPIcs.ITCS.2026.71},
  annote =	{Keywords: FSS, Data Structures, Lower Bounds, Black-Box Reductions}
}
Document
DOI: 10.4230/LIPIcs.DISC.2025.42
Kudzu: Fast and Simple High-Throughput BFT

Authors: Victor Shoup, Jakub Sliwinski, and Yann Vonlanthen

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

Abstract
We present Kudzu, a high-throughput atomic broadcast protocol with an integrated fast path. Our contribution is based on the combination of two lines of work. Firstly, our protocol achieves finality in just two rounds of communication if all but p out of n = 3f + 2p + 1 participating replicas behave correctly, where f is the number of Byzantine faults that are tolerated. Due to the seamless integration of the fast path, even in the presence of more than p faults, our protocol maintains state-of-the-art characteristics. Secondly, our protocol utilizes the bandwidth of participating replicas in a balanced way, alleviating the bottleneck at the leader, and thus enabling high throughput. This is achieved by disseminating blocks using erasure codes. Despite combining a novel set of advantages, Kudzu is remarkably simple: intricacies such as "progress certificates", complex view changes, and speculative execution are avoided.
Cite as

Victor Shoup, Jakub Sliwinski, and Yann Vonlanthen. Kudzu: Fast and Simple High-Throughput BFT. In 39th International Symposium on Distributed Computing (DISC 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 356, pp. 42:1-42:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{shoup_et_al:LIPIcs.DISC.2025.42,
  author =	{Shoup, Victor and Sliwinski, Jakub and Vonlanthen, Yann},
  title =	{{Kudzu: Fast and Simple High-Throughput BFT}},
  booktitle =	{39th International Symposium on Distributed Computing (DISC 2025)},
  pages =	{42:1--42:19},
  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.2025.42},
  URN =		{urn:nbn:de:0030-drops-248597},
  doi =		{10.4230/LIPIcs.DISC.2025.42},
  annote =	{Keywords: Consensus, Blockchain, Byzantine Fault Tolerance, Fast Path, State Machine Replication}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.4
Proxying Is Enough: Security of Proxying in TLS Oracles and AEAD Context Unforgeability

Authors: Zhongtang Luo, Yanxue Jia, Yaobin Shen, and Aniket Kate

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

Abstract
TLS allows a client to securely obtain data from a server, but does not allow the client to offer the data provenance to an external node. TLS oracle protocols are used to solve the problem. Specifically, the verifier node, as an external node, is convinced that the data is indeed coming from a pre-defined TLS server, while remaining unable to access the client’s credentials (e.g., password). Previous TLS oracle protocols such as DECO (CCS 2020) enforced the communication pattern of server-client-verifier and utilized a novel three-party handshake process during TLS to ensure data integrity against potential tempering by the client. However, this approach introduces a significant performance penalty on the client and the verifier. Most recently, some works have proposed to reduce the overhead by putting the verifier (as a proxy) between the server and the client such that the correct TLS transcript is available to the verifier. Nevertheless, these works still rely on heavy two-party secure computations or zero-knowledge proofs. In this work, we push the proxy model to the extreme, where the verifier only needs to forward messages without performing any other heavy computational operations when only the credentials should be protected and the data retrieved from the server could be open to the verifier. Surprisingly, we prove that the thorough proxy model is enough to guarantee security in some common scenarios, allowing a saving of 60-90% in running time under common scenarios. We first formalize the proxy-based Oracle protocol and functionality that allows the verifier to directly proxy client-server TLS communication, without entering a three-party handshake or interfering with the connection in any way. We then show that for common TLS-based higher-level protocols such as HTTPS, data integrity to the verifier proxy is ensured by the variable padding built into the HTTP protocol semantics. On the other hand, if a TLS-based protocol comes without variable padding, we demonstrate that data integrity cannot be guaranteed. In this context, we then study the case where the TLS response is pre-determined and cannot be tampered with during the connection. We propose the concept of context unforgeability and show that data integrity can also be guaranteed as long as the underlying Authenticated Encryption with Associated Data (AEAD) satisfies context unforgeability. We further show that ChaCha20-Poly1305 satisfies the concept while AES-GCM does not.
Cite as

Zhongtang Luo, Yanxue Jia, Yaobin Shen, and Aniket Kate. Proxying Is Enough: Security of Proxying in TLS Oracles and AEAD Context Unforgeability. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 4:1-4:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{luo_et_al:LIPIcs.AFT.2025.4,
  author =	{Luo, Zhongtang and Jia, Yanxue and Shen, Yaobin and Kate, Aniket},
  title =	{{Proxying Is Enough: Security of Proxying in TLS Oracles and AEAD Context Unforgeability}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{4:1--4:24},
  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.2025.4},
  URN =		{urn:nbn:de:0030-drops-247231},
  doi =		{10.4230/LIPIcs.AFT.2025.4},
  annote =	{Keywords: Oracle, TLS, AEAD, Key Commitment}
}
Document
DOI: 10.4230/LIPIcs.AFT.2025.31
Trustless Bridges via Random Sampling Light Clients

Authors: Bhargav Nagaraja Bhatt, Fatemeh Shirazi, and Alistair Stewart

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

Abstract
The increasing number of blockchain projects introduced annually has led to a pressing need for secure and efficient interoperability solutions. Currently, the lack of such solutions forces end-users to rely on centralized intermediaries, contradicting the core principle of decentralization and trust minimization in blockchain technology. We propose a decentralized and efficient interoperability solution (aka Bridge Protocol) that operates without additional trust assumptions, relying solely on the Byzantine Fault Tolerance (BFT) properties of the two chains being connected. In particular, relayers (actors that exchange messages between networks) are permissionless and decentralized, hence eliminating any single point of failure. We introduce Random Sampling, a novel technique for on-chain light clients to efficiently follow the history of PoS blockchains by reducing the signature verifications required. Here, the randomness is drawn on-chain, for example, using Ethereum’s RANDAO. We analyze the security of the bridge from a crypto- economic perspective and provide a framework to derive the security parameters. This includes handling subtle concurrency issues and randomness bias in strawman designs. While the protocol is applicable to various PoS chains, we demonstrate the protocol’s practical feasibility by showcasing an instantiated bridge between Polkadot and Ethereum (currently deployed), and discuss some practical security challenges. Furthermore, we evaluate the efficiency of our on-chain light client verifier (implemented as an Ethereum smart contract) against SNARK-based approaches, demonstrating significantly lower gas costs for signature verification - even for validator sets up to 10⁶.
Cite as

Bhargav Nagaraja Bhatt, Fatemeh Shirazi, and Alistair Stewart. Trustless Bridges via Random Sampling Light Clients. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 31:1-31:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bhatt_et_al:LIPIcs.AFT.2025.31,
  author =	{Bhatt, Bhargav Nagaraja and Shirazi, Fatemeh and Stewart, Alistair},
  title =	{{Trustless Bridges via Random Sampling Light Clients}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{31:1--31:24},
  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.2025.31},
  URN =		{urn:nbn:de:0030-drops-247503},
  doi =		{10.4230/LIPIcs.AFT.2025.31},
  annote =	{Keywords: PoS Blockchains, Trustless Bridges, Light Clients, Decentralised Relayers, RANDAO Bias}
}
Document
DOI: 10.4230/LIPIcs.ITP.2025.23
Formalizing the Hidden Number Problem in Isabelle/HOL

Authors: Sage Binder, Eric Ren, and Katherine Kosaian

Published in: LIPIcs, Volume 352, 16th International Conference on Interactive Theorem Proving (ITP 2025)

Abstract
We formalize the hidden number problem (HNP), as introduced in a seminal work by Boneh and Venkatesan in 1996, in Isabelle/HOL. Intuitively, the HNP involves demonstrating the existence of an algorithm (the "adversary") which can compute (with high probability) a hidden number α given access to a bit-leaking oracle. Originally developed to establish the security of Diffie-Hellman key exchange, the HNP has since been used not only for protocol security but also in cryptographic attacks, including notable ones on DSA and ECDSA. Further, as the HNP establishes an expressive paradigm for reasoning about security in the context of information leakage, many HNP variants for other specialized cryptographic applications have since been developed. A main contribution of our work is explicating and clarifying the HNP proof blueprint from the original source material; naturally, formalization forces us to make all assumptions and proof steps precise and transparent. For example, the source material did not explicitly define the adversary and only abstractly defined what information is being leaked; our formalization concretizes both definitions. Additionally, the HNP makes use of an instance of Babai’s nearest plane algorithm, which solves the approximate closest vector problem; we formalize this as a result of independent interest. Our formalizations of Babai’s algorithm and the HNP adversary are executable, setting up potential future work, e.g. in developing formally verified instances of cryptographic attacks.
Cite as

Sage Binder, Eric Ren, and Katherine Kosaian. Formalizing the Hidden Number Problem in Isabelle/HOL. In 16th International Conference on Interactive Theorem Proving (ITP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 352, pp. 23:1-23:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{binder_et_al:LIPIcs.ITP.2025.23,
  author =	{Binder, Sage and Ren, Eric and Kosaian, Katherine},
  title =	{{Formalizing the Hidden Number Problem in Isabelle/HOL}},
  booktitle =	{16th International Conference on Interactive Theorem Proving (ITP 2025)},
  pages =	{23:1--23:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-396-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{352},
  editor =	{Forster, Yannick and Keller, Chantal},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2025.23},
  URN =		{urn:nbn:de:0030-drops-246216},
  doi =		{10.4230/LIPIcs.ITP.2025.23},
  annote =	{Keywords: hidden number problem, Babai’s nearest plane algorithm, cryptography, interactive theorem proving, Isabelle/HOL}
}
Document
Tool Paper
DOI: 10.4230/OASIcs.FMBC.2025.13
A Benchmark Framework for Byzantine Fault Tolerance Testing Algorithms (Tool Paper)

Authors: João Miguel Louro Neto and Burcu Kulahcioglu Ozkan

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

Abstract
Recent discoveries of vulnerabilities in the design and implementation of Byzantine fault-tolerant protocols underscore the need for testing and exploration techniques to ensure their correctness. While there has been some recent effort for automated test generation for BFT protocols, there is no benchmark framework available to systematically evaluate their performance. We present ByzzBench, a benchmark framework designed to evaluate the performance of testing algorithms in detecting Byzantine fault tolerance bugs. ByzzBench is designed for a standardized implementation of BFT protocols and their execution in a controlled testing environment. It controls the nondeterminism in the concurrency, network, and process faults in the protocol execution, enabling the functionality to enforce particular execution scenarios and thereby facilitating the implementation of testing algorithms for BFT protocols.
Cite as

João Miguel Louro Neto and Burcu Kulahcioglu Ozkan. A Benchmark Framework for Byzantine Fault Tolerance Testing Algorithms (Tool Paper). In 6th International Workshop on Formal Methods for Blockchains (FMBC 2025). Open Access Series in Informatics (OASIcs), Volume 129, pp. 13:1-13:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{louroneto_et_al:OASIcs.FMBC.2025.13,
  author =	{Louro Neto, Jo\~{a}o Miguel and Kulahcioglu Ozkan, Burcu},
  title =	{{A Benchmark Framework for Byzantine Fault Tolerance Testing Algorithms}},
  booktitle =	{6th International Workshop on Formal Methods for Blockchains (FMBC 2025)},
  pages =	{13:1--13:11},
  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.2025.13},
  URN =		{urn:nbn:de:0030-drops-230406},
  doi =		{10.4230/OASIcs.FMBC.2025.13},
  annote =	{Keywords: Byzantine Fault Tolerance, BFT Protocols, Automated Testing}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2024.20
How Robust Are Synchronous Consensus Protocols?

Authors: Nenad Milošević, Daniel Cason, Zarko Milošević, and Fernando Pedone

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

Abstract
Synchronous Byzantine fault-tolerant (BFT) protocols have long been a reality in an academic setting, yet their practicality remains debated. The main concern of skeptics of synchronous systems is that the correctness of these protocols depends on the timely delivery of all messages within a predefined synchronous bound, Δ. This dependency creates a challenging tradeoff between protocol correctness and performance, as Δ directly impacts both. In this paper, we examine this tradeoff in detail. Specifically, we introduce BoundBFT, a new synchronous BFT consensus protocol. We analyze how BoundBFT’s correctness can be compromised and use this analysis to design and implement the most effective attack strategies that malicious processes could employ. Furthermore, we experimentally determine the synchronous bound Δ that provides sufficient confidence in maintaining protocol correctness even in the presence of malicious replicas. Finally, we apply this discovered bound to BoundBFT, evaluate its performance, and compare it to state-of-the-art synchronous and partially synchronous protocols.
Cite as

Nenad Milošević, Daniel Cason, Zarko Milošević, and Fernando Pedone. How Robust Are Synchronous Consensus Protocols?. In 28th International Conference on Principles of Distributed Systems (OPODIS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 324, pp. 20:1-20:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{milosevic_et_al:LIPIcs.OPODIS.2024.20,
  author =	{Milo\v{s}evi\'{c}, Nenad and Cason, Daniel and Milo\v{s}evi\'{c}, Zarko and Pedone, Fernando},
  title =	{{How Robust Are Synchronous Consensus Protocols?}},
  booktitle =	{28th International Conference on Principles of Distributed Systems (OPODIS 2024)},
  pages =	{20:1--20:25},
  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.2024.20},
  URN =		{urn:nbn:de:0030-drops-225560},
  doi =		{10.4230/LIPIcs.OPODIS.2024.20},
  annote =	{Keywords: Synchronous Consensus, Byzantine Failures, Blockchain}
}
Document
DOI: 10.4230/DagRep.12.4.54
Digital Twins for Cyber-Physical Systems Security (Dagstuhl Seminar 22171)

Authors: Alvaro Cárdenas Mora, Simin Nadjm-Tehrani, Edgar Weippl, and Matthias Eckhart

Published in: Dagstuhl Reports, Volume 12, Issue 4 (2022)

Abstract
Cyber-physical systems (CPSs) may constitute an attractive attack target due to the increased networking of components that yields an expanded attack surface. If their physical control capabilities are compromised, safety implications may arise. Thus, it is vital that the CPSs being engineered are thoroughly tested and that adequate response measures can be realized upon detecting intruders during operation. However, security testing is hard to conduct due to expensive hardware, limited maintenance periods, and safety risks. Furthermore, the increased stealthiness of threat actors requires new intrusion detection and response methods. Interestingly, digital twins have become an important concept in industrial informatics to solve similar problems, yet with a non-security-related focus: Digital twins that virtually replicate the real systems provide cost-efficient modeling, testing, monitoring, and even predictive capabilities. However, until recently, the digital-twin concept has mainly focused on production optimizations or design improvements without considering its potential for CPS security. The Dagstuhl Seminar 22171 "Digital Twins for Cyber-Physical Systems Security" therefore aimed to serve as an interdisciplinary, open knowledge-sharing platform to investigate the benefits and challenges of applying the digital-twin concept to improve the security of CPSs.
Cite as

Alvaro Cárdenas Mora, Simin Nadjm-Tehrani, Edgar Weippl, and Matthias Eckhart. Digital Twins for Cyber-Physical Systems Security (Dagstuhl Seminar 22171). In Dagstuhl Reports, Volume 12, Issue 4, pp. 54-71, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{mora_et_al:DagRep.12.4.54,
  author =	{Mora, Alvaro C\'{a}rdenas and Nadjm-Tehrani, Simin and Weippl, Edgar and Eckhart, Matthias},
  title =	{{Digital Twins for Cyber-Physical Systems Security (Dagstuhl Seminar 22171)}},
  pages =	{54--71},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2022},
  volume =	{12},
  number =	{4},
  editor =	{Mora, Alvaro C\'{a}rdenas and Nadjm-Tehrani, Simin and Weippl, Edgar and Eckhart, Matthias},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.12.4.54},
  URN =		{urn:nbn:de:0030-drops-172805},
  doi =		{10.4230/DagRep.12.4.54},
  annote =	{Keywords: cyber-physical systems, digital twins, information security, production systems engineering, SCADA, industrial control systems, Industry 4.0}
}
Document
DOI: 10.4230/DagRep.11.10.36
Managing Industrial Control Systems Security Risks for Cyber Insurance (Dagstuhl Seminar 21451)

Authors: Simon Dejung, Mingyan Liu, Arndt Lüder, and Edgar Weippl

Published in: Dagstuhl Reports, Volume 11, Issue 10 (2022)

Abstract
Industrial control systems (ICSs), such as production systems or critical infrastructures, are an attractive target for cybercriminals, since attacks against these systems may cause severe physical damages/material damages (PD/MD), resulting in business interruption (BI) and loss of profit (LOP). Besides financial loss, cyber-attacks against ICSs can also harm human health or the environment or even be used as a kind of weapon. Thus, it is of utmost importance to manage cyber risks throughout the ICS’s lifecycle (i.e., engineering, operation, decommissioning), especially in light of the ever-increasing threat level that is accompanied by the progressive digitization of industrial processes. However, asset owners may not be able to address security risks sufficiently, nor adequately quantify them in terms of their potential impact (physical and non-physical) and likelihood. A self-deceptive solution might be using insurance to transfer these risks and offload them from their balance sheet since the underlying problem remains unsolved. The reason for this is that the exposure for asset owners remains and mitigation measures may still not be implemented adequately while the insurance industry is onboarding unassessed risks and covering it often without premium and without managing the potential exposure of accumulated events. The Dagstuhl Seminar 21451 "Managing Industrial Control Systems Security Risks for Cyber Insurance" aimed to provide an interdisciplinary forum to analyze and discuss open questions and current topics of research in this area in order to gain in-depth insights into the security risks of ICSs and the quantification thereof.
Cite as

Simon Dejung, Mingyan Liu, Arndt Lüder, and Edgar Weippl. Managing Industrial Control Systems Security Risks for Cyber Insurance (Dagstuhl Seminar 21451). In Dagstuhl Reports, Volume 11, Issue 10, pp. 36-56, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{dejung_et_al:DagRep.11.10.36,
  author =	{Dejung, Simon and Liu, Mingyan and L\"{u}der, Arndt and Weippl, Edgar},
  title =	{{Managing Industrial Control Systems Security Risks for Cyber Insurance (Dagstuhl Seminar 21451)}},
  pages =	{36--56},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2022},
  volume =	{11},
  number =	{10},
  editor =	{Dejung, Simon and Liu, Mingyan and L\"{u}der, Arndt and Weippl, Edgar},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.11.10.36},
  URN =		{urn:nbn:de:0030-drops-159273},
  doi =		{10.4230/DagRep.11.10.36},
  annote =	{Keywords: industrial control systems, security, cyber insurance, cyber risk quantification, production systems engineering, risk engineering, SCADA, Industry 4.0}
}
Document
DOI: 10.4230/OASIcs.Gabbrielli.2
A Formal Analysis of the Bitcoin Protocol

Authors: Cosimo Laneve and Adele Veschetti

Published in: OASIcs, Volume 86, Recent Developments in the Design and Implementation of Programming Languages (2020)

Abstract
We study Nakamoto’s Bitcoin protocol that implements a distributed ledger on peer-to-peer asynchronous networks. In particular, we define a principled formal model of key participants - the miners - as stochastic processes and describe the whole system as a parallel composition of miners. We therefore compute the probability that ledgers turn into a state with more severe inconsistencies, e.g. with longer forks, under the assumptions that messages are not lost and nodes are not hostile. We also study how the presence of hostile nodes mining blocks in wrong positions impacts on the consistency of the ledgers. Our theoretical results agree with the simulations performed on a probabilistic model checker that we extended with dynamic datatypes in order to have a faithful description of miners' behaviour.
Cite as

Cosimo Laneve and Adele Veschetti. A Formal Analysis of the Bitcoin Protocol. In Recent Developments in the Design and Implementation of Programming Languages. Open Access Series in Informatics (OASIcs), Volume 86, pp. 2:1-2:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{laneve_et_al:OASIcs.Gabbrielli.2,
  author =	{Laneve, Cosimo and Veschetti, Adele},
  title =	{{A Formal Analysis of the Bitcoin Protocol}},
  booktitle =	{Recent Developments in the Design and Implementation of Programming Languages},
  pages =	{2:1--2:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-171-9},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{86},
  editor =	{de Boer, Frank S. and Mauro, Jacopo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.Gabbrielli.2},
  URN =		{urn:nbn:de:0030-drops-132242},
  doi =		{10.4230/OASIcs.Gabbrielli.2},
  annote =	{Keywords: Bitcoin, Distributed consensus, Distributed ledgers, Blockchain, PRISM, forks}
}
Document
DOI: 10.4230/OASIcs.Gabbrielli.4
Towards a Unifying Framework for Tuning Analysis Precision by Program Transformation

Authors: Mila Dalla Preda

Published in: OASIcs, Volume 86, Recent Developments in the Design and Implementation of Programming Languages (2020)

Abstract
Static and dynamic program analyses attempt to extract useful information on program’s behaviours. Static analysis uses an abstract model of programs to reason on their runtime behaviour without actually running them, while dynamic analysis reasons on a test set of real program executions. For this reason, the precision of static analysis is limited by the presence of false positives (executions allowed by the abstract model that cannot happen at runtime), while the precision of dynamic analysis is limited by the presence of false negatives (real executions that are not in the test set). Researchers have developed many analysis techniques and tools in the attempt to increase the precision of program verification. Software protection is an interesting scenario where programs need to be protected from adversaries that use program analysis to understand their inner working and then exploit this knowledge to perform some illicit actions. Program analysis plays a dual role in program verification and software protection: in program verification we want the analysis to be as precise as possible, while in software protection we want to degrade the results of the analysis as much as possible. Indeed, in software protection researchers usually recur to a special class of program transformations, called code obfuscation, to modify a program in order to make it more difficult to analyse while preserving its intended functionality. In this setting, it is interesting to study how program transformations that preserve the intended behaviour of programs can affect the precision of both static and dynamic analysis. While some works have been done in order to formalise the efficiency of code obfuscation in degrading static analysis and in the possibility of transforming programs in order to avoid or increase false positives, less attention has been posed to formalise the relation between program transformations and false negatives in dynamic analysis. In this work we are setting the scene for a formal investigation of the syntactic and semantic program features that affect the presence of false negatives in dynamic analysis. We believe that this understanding would be useful for improving the precision of the existing dynamic analysis tools and in the design of program transformations that complicate the dynamic analysis. To Maurizio on his 60th birthday!
Cite as

Mila Dalla Preda. Towards a Unifying Framework for Tuning Analysis Precision by Program Transformation. In Recent Developments in the Design and Implementation of Programming Languages. Open Access Series in Informatics (OASIcs), Volume 86, pp. 4:1-4:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{dallapreda:OASIcs.Gabbrielli.4,
  author =	{Dalla Preda, Mila},
  title =	{{Towards a Unifying Framework for Tuning Analysis Precision by Program Transformation}},
  booktitle =	{Recent Developments in the Design and Implementation of Programming Languages},
  pages =	{4:1--4:22},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-171-9},
  ISSN =	{2190-6807},
  year =	{2020},
  volume =	{86},
  editor =	{de Boer, Frank S. and Mauro, Jacopo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.Gabbrielli.4},
  URN =		{urn:nbn:de:0030-drops-132263},
  doi =		{10.4230/OASIcs.Gabbrielli.4},
  annote =	{Keywords: Program analysis, analysis precision, program transformation, software protection, code obfuscation}
}
Document
DOI: 10.4230/DagRep.8.4.20
Blockchains, Smart Contracts and Future Applications (Dagstuhl Seminar 18152)

Authors: Foteini Baldimtsi, Stefan Katzenbeisser, Volkmar Lotz, and Edgar Weippl

Published in: Dagstuhl Reports, Volume 8, Issue 4 (2018)

Abstract
This report documents the Dagstuhl seminar 18152 "Blockchains, Smart Contracts & Future Applications". While Bitcoin currently works well in practice, there are many open questions regarding the long-term perspective of blockchain technologies, for both public and private/permissioned blockchains. It is yet unclear how processes can be designed to work in predictive ways and how to embed security in the lifecycle of smart contract development and deployment. Furthermore, the distributed nature of the system needs to be considered when thinking about which groups or individuals can influence future developments. Similar to 'real-world' societies, blockchains are based on mutual recognition of conventions. Diverse academic disciplines as well as industry can and need to collaborate to advance research in blockchain and to fully understand how the technology might impact our future lives.
Cite as

Foteini Baldimtsi, Stefan Katzenbeisser, Volkmar Lotz, and Edgar Weippl. Blockchains, Smart Contracts and Future Applications (Dagstuhl Seminar 18152). In Dagstuhl Reports, Volume 8, Issue 4, pp. 20-31, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@Article{baldimtsi_et_al:DagRep.8.4.20,
  author =	{Baldimtsi, Foteini and Katzenbeisser, Stefan and Lotz, Volkmar and Weippl, Edgar},
  title =	{{Blockchains, Smart Contracts and Future Applications (Dagstuhl Seminar 18152)}},
  pages =	{20--31},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2018},
  volume =	{8},
  number =	{4},
  editor =	{Baldimtsi, Foteini and Katzenbeisser, Stefan and Lotz, Volkmar and Weippl, Edgar},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.8.4.20},
  URN =		{urn:nbn:de:0030-drops-97597},
  doi =		{10.4230/DagRep.8.4.20},
  annote =	{Keywords: blockchains, consensus algorithms, cryptographic currency, incentive engineering, smart contracts}
}
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