8 Search Results for "Cortier, Véronique"

Document
DOI: 10.4230/LIPIcs.ITCS.2026.28
Linear Time Encodable Binary Code Achieving GV Bound with Linear Time Encodable Dual Achieving GV Bound

Authors: Martijn Brehm and Nicolas Resch

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

Abstract
We initiate the study of what we term "fast good codes" with "fast good duals." Specifically, we consider the task of constructing a binary linear code C ≤ 𝔽₂ⁿ such that both it and its dual C^⟂ : = {x ∈ 𝔽₂ⁿ:∀ c ∈ C, ⟨ x,c⟩ = 0} are asymptotically good (in fact, have rate-distance tradeoff approaching the GV bound), and are encodable in O(n) time. While we believe such codes should find applications more broadly, as motivation we describe how such codes can be used the secure computation task of encrypted matrix-vector product, as studied by Behhamouda et al (CCS 2025). Our main contribution is a construction of such a fast good code with fast good dual. Our construction is inspired by the repeat multiple accumulate (RMA) codes of Divsalar, Jin and McEliece (Allerton, 1998). To create the rate 1/2 code, after repeating each message coordinate, we perform accumulation steps - where first a uniform coordinate permutation is applied, and afterwards the prefix-sum modulo 2 is applied - which are alternated with discrete derivative steps - where again a uniform coordinate permutation is applied, and afterwards the previous two coordinates are summed modulo 2. Importantly, these two operations are inverse of each other. In particular, the dual of the code is very similar, with the accumulation and discrete derivative steps reversed. Our analysis is inspired by a prior analysis of RMA codes due to Ravazzi and Fagnani (IEEE Trans. Info. Theory, 2009). The main idea is to bound the input-output weight-enumerator function: the expected number of messages of a given weight that are encoded into a codeword of a given weight. We face new challenges in controlling the behaviour of the discrete derivative matrix (which can significantly drop the weight of a vector), which we overcome by careful case analysis.
Cite as

Martijn Brehm and Nicolas Resch. Linear Time Encodable Binary Code Achieving GV Bound with Linear Time Encodable Dual Achieving GV Bound. In 17th Innovations in Theoretical Computer Science Conference (ITCS 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 362, pp. 28:1-28:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{brehm_et_al:LIPIcs.ITCS.2026.28,
  author =	{Brehm, Martijn and Resch, Nicolas},
  title =	{{Linear Time Encodable Binary Code Achieving GV Bound with Linear Time Encodable Dual Achieving GV Bound}},
  booktitle =	{17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
  pages =	{28:1--28:19},
  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.2026.28},
  URN =		{urn:nbn:de:0030-drops-253157},
  doi =		{10.4230/LIPIcs.ITCS.2026.28},
  annote =	{Keywords: Binary error-correcting codes, dual codes, fast encoding, repeat-multiple-accumulate codes}
}
Document
DOI: 10.4230/LIPIcs.FSCD.2025.18
Knowledge Problems vs Unification and Matching: Dichotomy Results

Authors: Serdar Erbatur, Andrew M. Marshall, Paliath Narendran, and Christophe Ringeissen

Published in: LIPIcs, Volume 337, 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)

Abstract
The research area of cryptographic protocol analysis contains a number of innovative algorithms and procedures for checking various security properties of protocols. Most of these procedures focus on solving one of several "knowledge problems" that model intruder knowledge. Solving these problems can demonstrate the ability of the intruder to obtain some forbidden information of the protocol, such as secret keys. Two important examples of these problems are the deduction problem and the static equivalence problem. Deduction is concerned with the ability to derive a term from a set of terms (or knowledge) obtained from the observation of a protocol instance. Static equivalence, on the other hand, is concerned with distinguishing between two runs of a protocol based on two sets of knowledge. These two knowledge problems at first inspection appear to be very close to the older automated reasoning problems of matching and unification. However, this first impression is wrong, and there have been a few results that have shown theories where one problem, such as unification, is undecidable but another problem, such as deduction, is decidable. These existing dichotomy results were, however, incomplete, and not all cases had been examined, thus leaving the possibility of some connection between the problems for those unexamined cases. In this paper, we consider the missing dichotomy cases. For each of the remaining cases, we demonstrate a theory that separates the two problems. In addition, once the dichotomy results are completed, it leaves open the question of the existence of non-trivial classes of theories for which all four of the problems are decidable. One example for which this is true is the well-known class of subterm convergent term rewrite systems. In this paper, we develop another example, a class of restrictive permutative theories for which all problems are likewise decidable.
Cite as

Serdar Erbatur, Andrew M. Marshall, Paliath Narendran, and Christophe Ringeissen. Knowledge Problems vs Unification and Matching: Dichotomy Results. In 10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 337, pp. 18:1-18:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{erbatur_et_al:LIPIcs.FSCD.2025.18,
  author =	{Erbatur, Serdar and Marshall, Andrew M. and Narendran, Paliath and Ringeissen, Christophe},
  title =	{{Knowledge Problems vs Unification and Matching: Dichotomy Results}},
  booktitle =	{10th International Conference on Formal Structures for Computation and Deduction (FSCD 2025)},
  pages =	{18:1--18:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-374-4},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{337},
  editor =	{Fern\'{a}ndez, Maribel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2025.18},
  URN =		{urn:nbn:de:0030-drops-236331},
  doi =		{10.4230/LIPIcs.FSCD.2025.18},
  annote =	{Keywords: Knowledge Problems, Unification, Matching, Decidability}
}
Document
DOI: 10.4230/LIPIcs.CSL.2025.24
Propositional Logics of Overwhelming Truth

Authors: Thibaut Antoine and David Baelde

Published in: LIPIcs, Volume 326, 33rd EACSL Annual Conference on Computer Science Logic (CSL 2025)

Abstract
Cryptographers consider that asymptotic security holds when, for any possible attacker running in polynomial time, the probability that the attack succeeds is negligible, i.e. that it tends fast enough to zero with the size of secrets. In order to reason formally about cryptographic truth, one may thus consider logics where a formula is satisfied when it is true with overwhelming probability, i.e. a probability that tends fast enough to one with the size of secrets. In such logics it is not always the case that either ϕ or ⌝ϕ is satisfied by a given model. However, security analyses will inevitably involve specific formulas, which we call determined, satisfying this property - typically because they are not probabilistic. The Squirrel proof assistant, which implements a logic of overwhelming truth, features ad-hoc proof rules for this purpose. In this paper, we study several propositional logics whose semantics rely on overwhelming truth. We first consider a modal logic of overwhelming truth, and show that it coincides with S5. In addition to providing an axiomatization, this brings a well-behaved proof system for our logic in the form of Poggiolesi’s hypersequent calculus. Further, we show that this system can be adapted to elegantly incorporate reasoning on determined atoms. We then consider a logic that is closer to Squirrel’s language, where the overwhelming truth modality cannot be nested. In that case, we show that a simple proof system, based on regular sequents, is sound and complete. This result justifies the core of Squirrel’s proof system.
Cite as

Thibaut Antoine and David Baelde. Propositional Logics of Overwhelming Truth. In 33rd EACSL Annual Conference on Computer Science Logic (CSL 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 326, pp. 24:1-24:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{antoine_et_al:LIPIcs.CSL.2025.24,
  author =	{Antoine, Thibaut and Baelde, David},
  title =	{{Propositional Logics of Overwhelming Truth}},
  booktitle =	{33rd EACSL Annual Conference on Computer Science Logic (CSL 2025)},
  pages =	{24:1--24:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-362-1},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{326},
  editor =	{Endrullis, J\"{o}rg and Schmitz, Sylvain},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2025.24},
  URN =		{urn:nbn:de:0030-drops-227818},
  doi =		{10.4230/LIPIcs.CSL.2025.24},
  annote =	{Keywords: Cryptography, Modal Logic, Sequent Calculus}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2020.31
Decidable Inductive Invariants for Verification of Cryptographic Protocols with Unbounded Sessions

Authors: Emanuele D'Osualdo and Felix Stutz

Published in: LIPIcs, Volume 171, 31st International Conference on Concurrency Theory (CONCUR 2020)

Abstract
We develop a theory of decidable inductive invariants for an infinite-state variant of the Applied πcalc, with applications to automatic verification of stateful cryptographic protocols with unbounded sessions/nonces. Since the problem is undecidable in general, we introduce depth-bounded protocols, a strict generalisation of a class from the literature, for which our decidable analysis is sound and complete. Our core contribution is a procedure to check that an invariant is inductive, which implies that every reachable configuration satisfies it. Our invariants can capture security properties like secrecy, can be inferred automatically, and represent an independently checkable certificate of correctness. We provide a prototype implementation and we report on its performance on some textbook examples.
Cite as

Emanuele D'Osualdo and Felix Stutz. Decidable Inductive Invariants for Verification of Cryptographic Protocols with Unbounded Sessions. In 31st International Conference on Concurrency Theory (CONCUR 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 171, pp. 31:1-31:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{dosualdo_et_al:LIPIcs.CONCUR.2020.31,
  author =	{D'Osualdo, Emanuele and Stutz, Felix},
  title =	{{Decidable Inductive Invariants for Verification of Cryptographic Protocols with Unbounded Sessions}},
  booktitle =	{31st International Conference on Concurrency Theory (CONCUR 2020)},
  pages =	{31:1--31:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-160-3},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{171},
  editor =	{Konnov, Igor and Kov\'{a}cs, Laura},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2020.31},
  URN =		{urn:nbn:de:0030-drops-128433},
  doi =		{10.4230/LIPIcs.CONCUR.2020.31},
  annote =	{Keywords: Security Protocols, Infinite-State Verification, Ideal Completions for WSTS}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.CSL.2020.1
Verification of Security Protocols (Invited Talk)

Authors: Véronique Cortier

Published in: LIPIcs, Volume 152, 28th EACSL Annual Conference on Computer Science Logic (CSL 2020)

Abstract
Cryptographic protocols aim at securing communications over insecure networks like the Internet. Over the past decades, numerous decision procedures and tools have been developed to automatically analyse the security of protocols. The field has now reached a good level of maturity with efficient techniques for the automatic security analysis of protocols After an overview of some famous protocols and flaws, we will describe the current techniques for security protocols analysis, often based on logic, and review the key challenges towards a fully automated verification.
Cite as

Véronique Cortier. Verification of Security Protocols (Invited Talk). In 28th EACSL Annual Conference on Computer Science Logic (CSL 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 152, pp. 1:1-1:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{cortier:LIPIcs.CSL.2020.1,
  author =	{Cortier, V\'{e}ronique},
  title =	{{Verification of Security Protocols}},
  booktitle =	{28th EACSL Annual Conference on Computer Science Logic (CSL 2020)},
  pages =	{1:1--1:2},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-132-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{152},
  editor =	{Fern\'{a}ndez, Maribel and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2020.1},
  URN =		{urn:nbn:de:0030-drops-116447},
  doi =		{10.4230/LIPIcs.CSL.2020.1},
  annote =	{Keywords: Security protocols, automated deduction, security}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2015.575
Secure Refinements of Communication Channels

Authors: Vincent Cheval, Véronique Cortier, and Eric le Morvan

Published in: LIPIcs, Volume 45, 35th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2015)

Abstract
It is a common practice to design a protocol (say Q) assuming some secure channels. Then the secure channels are implemented using any standard protocol, e.g. TLS. In this paper, we study when such a practice is indeed secure. We provide a characterization of both confidential and authenticated channels. As an application, we study several protocols of the literature including TLS and BAC protocols. Thanks to our result, we can consider a larger number of sessions when analyzing complex protocols resulting from explicit implementation of the secure channels of some more abstract protocol Q.
Cite as

Vincent Cheval, Véronique Cortier, and Eric le Morvan. Secure Refinements of Communication Channels. In 35th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 45, pp. 575-589, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{cheval_et_al:LIPIcs.FSTTCS.2015.575,
  author =	{Cheval, Vincent and Cortier, V\'{e}ronique and le Morvan, Eric},
  title =	{{Secure Refinements of Communication Channels}},
  booktitle =	{35th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2015)},
  pages =	{575--589},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-97-2},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{45},
  editor =	{Harsha, Prahladh and Ramalingam, G.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2015.575},
  URN =		{urn:nbn:de:0030-drops-56583},
  doi =		{10.4230/LIPIcs.FSTTCS.2015.575},
  annote =	{Keywords: Protocol, Composition, Formal methods, Channels, Implementation}
}
Document
DOI: 10.4230/LIPIcs.STACS.2011.29
How to prove security of communication protocols? A discussion on the soundness of formal models w.r.t. computational ones.

Authors: Hubert Comon-Lundh and Véronique Cortier

Published in: LIPIcs, Volume 9, 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)

Abstract
Security protocols are short programs that aim at securing communication over a public network. Their design is known to be error-prone with flaws found years later. That is why they deserve a careful security analysis, with rigorous proofs. Two main lines of research have been (independently) developed to analyse the security of protocols. On the one hand, formal methods provide with symbolic models and often automatic proofs. On the other hand, cryptographic models propose a tighter modeling but proofs are more difficult to write and to check. An approach developed during the last decade consists in bridging the two approaches, showing that symbolic models are sound w.r.t. symbolic ones, yielding strong security guarantees using automatic tools. These results have been developed for several cryptographic primitives (e.g. symmetric and asymmetric encryption, signatures, hash) and security properties. While proving soundness of symbolic models is a very promising approach, several technical details are often not satisfactory. Focusing on symmetric encryption, we describe the difficulties and limitations of the available results.
Cite as

Hubert Comon-Lundh and Véronique Cortier. How to prove security of communication protocols? A discussion on the soundness of formal models w.r.t. computational ones.. In 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 9, pp. 29-44, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)

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@InProceedings{comonlundh_et_al:LIPIcs.STACS.2011.29,
  author =	{Comon-Lundh, Hubert and Cortier, V\'{e}ronique},
  title =	{{How to prove security of communication protocols? A discussion on the soundness of formal models w.r.t. computational ones.}},
  booktitle =	{28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011)},
  pages =	{29--44},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-25-5},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{9},
  editor =	{Schwentick, Thomas and D\"{u}rr, Christoph},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2011.29},
  URN =		{urn:nbn:de:0030-drops-29993},
  doi =		{10.4230/LIPIcs.STACS.2011.29},
  annote =	{Keywords: verification, security, cryptography}
}
Document
DOI: 10.4230/OASIcs.TrustworthySW.2006.691
Relating two standard notions of secrecy

Authors: Eugen Zalinescu, Véronique Cortier, and Michaël Rusinowitch

Published in: OASIcs, Volume 3, Workshop on Trustworthy Software (2006)

Abstract
Two styles of definitions are usually considered to express that a security protocol preserves the confidentiality of a data { t s}. Reach-ability-based secrecy means that { t s} should never be disclosed while equi-valence-based secrecy states that two executions of a protocol with distinct instances for { t s} should be indistinguishable to an attacker. Although the second formulation ensures a higher level of security and is closer to cryptographic notions of secrecy, decidability results and automatic tools have mainly focused on the first definition so far. This paper initiates a systematic investigation of situations where syntactic secrecy entails strong secrecy. We show that in the passive case, reachability-based secrecy actually implies equivalence-based secrecy for signatures, symmetric and asymmetric encryption provided that the primitives are probabilistic. For active adversaries in the case of symmetric encryption, we provide sufficient (and rather tight) conditions on the protocol for this implication to hold.
Cite as

Eugen Zalinescu, Véronique Cortier, and Michaël Rusinowitch. Relating two standard notions of secrecy. In Workshop on Trustworthy Software. Open Access Series in Informatics (OASIcs), Volume 3, pp. 1-29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{zalinescu_et_al:OASIcs.TrustworthySW.2006.691,
  author =	{Zalinescu, Eugen and Cortier, V\'{e}ronique and Rusinowitch, Micha\"{e}l},
  title =	{{Relating two standard notions of secrecy}},
  booktitle =	{Workshop on Trustworthy Software},
  pages =	{1--29},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-02-6},
  ISSN =	{2190-6807},
  year =	{2006},
  volume =	{3},
  editor =	{Autexier, Serge and Merz, Stephan and van der Torre, Leon and Wilhelm, Reinhard and Wolper, Pierre},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.TrustworthySW.2006.691},
  URN =		{urn:nbn:de:0030-drops-6911},
  doi =		{10.4230/OASIcs.TrustworthySW.2006.691},
  annote =	{Keywords: Verification, security protocols, secrecy, applied-pi calculus}
}
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