4 Search Results for "Delignat-Lavaud, Antoine"

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.2025.15
Beyond Optimal Fault-Tolerance

Authors: Andrew Lewis-Pye and Tim Roughgarden

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

Abstract
One of the most basic properties of a consensus protocol is its fault-tolerance - the maximum fraction of faulty participants that the protocol can tolerate without losing fundamental guarantees such as safety and liveness. Because of its importance, the optimal fault-tolerance achievable by any protocol has been characterized in a wide range of settings. For example, for state machine replication (SMR) protocols operating in the partially synchronous setting, it is possible to simultaneously guarantee consistency against α-bounded adversaries (i.e., adversaries that control less than an α fraction of the participants) and liveness against β-bounded adversaries if and only if α + 2β ≤ 1. This paper characterizes to what extent "better-than-optimal" fault-tolerance guarantees are possible for SMR protocols when the standard consistency requirement is relaxed to allow a bounded number r of consistency violations, each potentially leading to the rollback of recently finalized transactions. We prove that bounded rollback is impossible without additional timing assumptions and investigate protocols that tolerate and recover from consistency violations whenever message delays around the time of an attack are bounded by a parameter Δ^* (which may be arbitrarily larger than the parameter Δ that bounds post-GST message delays in the partially synchronous model). Here, a protocol’s fault-tolerance can be a non-constant function of r, and we prove, for each r, matching upper and lower bounds on the optimal "recoverable fault-tolerance" achievable by any SMR protocol. For example, for protocols that guarantee liveness against 1/3-bounded adversaries in the partially synchronous setting, a 5/9-bounded adversary can always cause one consistency violation but not two, and a 2/3-bounded adversary can always cause two consistency violations but not three. Our positive results are achieved through a generic "recovery procedure" that can be grafted on to any accountable SMR protocol and restores consistency following a violation while rolling back only transactions that were finalized in the previous 2Δ^* timesteps.
Cite as

Andrew Lewis-Pye and Tim Roughgarden. Beyond Optimal Fault-Tolerance. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 15:1-15:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{lewispye_et_al:LIPIcs.AFT.2025.15,
  author =	{Lewis-Pye, Andrew and Roughgarden, Tim},
  title =	{{Beyond Optimal Fault-Tolerance}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{15:1--15:23},
  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.2025.15},
  URN =		{urn:nbn:de:0030-drops-247341},
  doi =		{10.4230/LIPIcs.AFT.2025.15},
  annote =	{Keywords: Distributed computing, consensus, recovery}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2025.32
Compositional Static Value Analysis for Higher-Order Numerical Programs

Authors: Milla Valnet, Raphaël Monat, and Antoine Miné

Published in: LIPIcs, Volume 333, 39th European Conference on Object-Oriented Programming (ECOOP 2025)

Abstract
Static analyzers have been successfully developed to detect runtime errors in many languages. However, the automatic analysis of functional languages remains a challenge due to their recursive functions, recursive algebraic data types, and higher-order functions. Classic type systems provide compositional methods that are in general not precise enough to prove the absence of runtime errors such as assertion failures. At the other end of the spectrum, deductive methods are more expressive but may require user guidance to prove invariants. Our work describes a static value analysis by abstract interpretation for a higher-order pure functional language. This analysis provides a sound and automatic approach to discover invariants and prevent assertion and match failures. We have designed a compositional analysis: functions are analyzed only once, at their definition site, generating a summary of their behavior. The summaries can be viewed as input-output relations expressed with relational abstract domains. We present two new abstract domains. A first abstract domain summarizes recursive algebraic data types. A second abstract domain lifts existing disjunctive relational summaries to higher-order by formalizing them as domains able to abstract higher-order functions. Both abstractions are parameterized by the abstractions of basic types (strings, integers, ...). Thanks to this parametric nature, both domains can be combined, allowing the analysis of higher-order functions manipulating algebraic data types and, conversely, algebraic data types using functions as first-class values. We have implemented this analysis in the open-source MOPSA platform. Preliminary evaluation confirms the precision of our approach on a set of 40 handwritten toy programs as well as 20 programs from the state-of-the-art Salto analyzer benchmark.
Cite as

Milla Valnet, Raphaël Monat, and Antoine Miné. Compositional Static Value Analysis for Higher-Order Numerical Programs. In 39th European Conference on Object-Oriented Programming (ECOOP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 333, pp. 32:1-32:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{valnet_et_al:LIPIcs.ECOOP.2025.32,
  author =	{Valnet, Milla and Monat, Rapha\"{e}l and Min\'{e}, Antoine},
  title =	{{Compositional Static Value Analysis for Higher-Order Numerical Programs}},
  booktitle =	{39th European Conference on Object-Oriented Programming (ECOOP 2025)},
  pages =	{32:1--32:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-373-7},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{333},
  editor =	{Aldrich, Jonathan and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2025.32},
  URN =		{urn:nbn:de:0030-drops-233249},
  doi =		{10.4230/LIPIcs.ECOOP.2025.32},
  annote =	{Keywords: Static Value Analysis, Functional Programming, Abstract Interpretation}
}
Document
DOI: 10.4230/LIPIcs.SNAPL.2017.1
Everest: Towards a Verified, Drop-in Replacement of HTTPS

Authors: Karthikeyan Bhargavan, Barry Bond, Antoine Delignat-Lavaud, Cédric Fournet, Chris Hawblitzel, Catalin Hritcu, Samin Ishtiaq, Markulf Kohlweiss, Rustan Leino, Jay Lorch, Kenji Maillard, Jianyang Pan, Bryan Parno, Jonathan Protzenko, Tahina Ramananandro, Ashay Rane, Aseem Rastogi, Nikhil Swamy, Laure Thompson, Peng Wang, Santiago Zanella-Béguelin, and Jean-Karim Zinzindohoué

Published in: LIPIcs, Volume 71, 2nd Summit on Advances in Programming Languages (SNAPL 2017)

Abstract
The HTTPS ecosystem is the foundation on which Internet security is built. At the heart of this ecosystem is the Transport Layer Security (TLS) protocol, which in turn uses the X.509 public-key infrastructure and numerous cryptographic constructions and algorithms. Unfortunately, this ecosystem is extremely brittle, with headline-grabbing attacks and emergency patches many times a year. We describe our ongoing efforts in Everest (The Everest VERified End-to-end Secure Transport) a project that aims to build and deploy a verified version of TLS and other components of HTTPS, replacing the current infrastructure with proven, secure software. Aiming both at full verification and usability, we conduct high-level code-based, game-playing proofs of security on cryptographic implementations that yield efficient, deployable code, at the level of C and assembly. Concretely, we use F*, a dependently typed language for programming, meta-programming, and proving at a high level, while relying on low-level DSLs embedded within F* for programming low-level components when necessary for performance and, sometimes, side-channel resistance. To compose the pieces, we compile all our code to source-like C and assembly, suitable for deployment and integration with existing code bases, as well as audit by independent security experts. Our main results so far include (1) the design of Low*, a subset of F* designed for C-like imperative programming but with high-level verification support, and KreMLin, a compiler that extracts Low* programs to C; (2) an implementation of the TLS-1.3 record layer in Low*, together with a proof of its concrete cryptographic security; (3) Vale, a new DSL for verified assembly language, and several optimized cryptographic primitives proven functionally correct and side-channel resistant. In an early deployment, all our verified software is integrated and deployed within libcurl, a widely used library of networking protocols.
Cite as

Karthikeyan Bhargavan, Barry Bond, Antoine Delignat-Lavaud, Cédric Fournet, Chris Hawblitzel, Catalin Hritcu, Samin Ishtiaq, Markulf Kohlweiss, Rustan Leino, Jay Lorch, Kenji Maillard, Jianyang Pan, Bryan Parno, Jonathan Protzenko, Tahina Ramananandro, Ashay Rane, Aseem Rastogi, Nikhil Swamy, Laure Thompson, Peng Wang, Santiago Zanella-Béguelin, and Jean-Karim Zinzindohoué. Everest: Towards a Verified, Drop-in Replacement of HTTPS. In 2nd Summit on Advances in Programming Languages (SNAPL 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 71, pp. 1:1-1:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{bhargavan_et_al:LIPIcs.SNAPL.2017.1,
  author =	{Bhargavan, Karthikeyan and Bond, Barry and Delignat-Lavaud, Antoine and Fournet, C\'{e}dric and Hawblitzel, Chris and Hritcu, Catalin and Ishtiaq, Samin and Kohlweiss, Markulf and Leino, Rustan and Lorch, Jay and Maillard, Kenji and Pan, Jianyang and Parno, Bryan and Protzenko, Jonathan and Ramananandro, Tahina and Rane, Ashay and Rastogi, Aseem and Swamy, Nikhil and Thompson, Laure and Wang, Peng and Zanella-B\'{e}guelin, Santiago and Zinzindohou\'{e}, Jean-Karim},
  title =	{{Everest: Towards a Verified, Drop-in Replacement of HTTPS}},
  booktitle =	{2nd Summit on Advances in Programming Languages (SNAPL 2017)},
  pages =	{1:1--1:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-032-3},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{71},
  editor =	{Lerner, Benjamin S. and Bod{\'\i}k, Rastislav and Krishnamurthi, Shriram},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SNAPL.2017.1},
  URN =		{urn:nbn:de:0030-drops-71196},
  doi =		{10.4230/LIPIcs.SNAPL.2017.1},
  annote =	{Keywords: Security, Cryptography, Verification, TLS}
}
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