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Documents authored by Maillard, Kenji

Document
DOI: 10.4230/LIPIcs.FSCD.2026.26
Divide and Check: Logical Relations, No Algorithms Attached

Authors: Josselin Poiret, Kenji Maillard, and Nicolas Tabareau

Published in: LIPIcs, Volume 378, 11th International Conference on Formal Structures for Computation and Deduction (FSCD 2026)

Abstract
The correctness of type-checking implementations for proof assistants based on dependent type theory relies on metatheoretical properties that ensure the decidability of typing, some of which require substantial logical strength. Recent mechanizations of such algorithms have highlighted the importance of separating the algorithmic components of the proof - often intricate but requiring relatively low logical strength - from the logical components, which depend on stronger metatheoretical properties, such as normalization or the injectivity of type constructors. In this work, we revisit the logical relations technique and show how it can be used to derive these metatheoretical properties in a direct and uniform way for a core dependent type theory featuring Π-types, N, ⊥ and a universe U. Our presentation yields a compact and conceptually simplified argument that isolates the logically strong reasoning from the algorithmic core. We argue that this approach scales smoothly to richer type theories, and demonstrate this by extending our construction to Exceptional Type Theory (ExcTT), obtaining the first mechanized canonicity proof for this theory.
Cite as

Josselin Poiret, Kenji Maillard, and Nicolas Tabareau. Divide and Check: Logical Relations, No Algorithms Attached. In 11th International Conference on Formal Structures for Computation and Deduction (FSCD 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 378, pp. 26:1-26:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{poiret_et_al:LIPIcs.FSCD.2026.26,
  author =	{Poiret, Josselin and Maillard, Kenji and Tabareau, Nicolas},
  title =	{{Divide and Check: Logical Relations, No Algorithms Attached}},
  booktitle =	{11th International Conference on Formal Structures for Computation and Deduction (FSCD 2026)},
  pages =	{26:1--26:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-433-8},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{378},
  editor =	{Pfenning, Frank},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2026.26},
  URN =		{urn:nbn:de:0030-drops-263764},
  doi =		{10.4230/LIPIcs.FSCD.2026.26},
  annote =	{Keywords: Type Theory, Proof Assistants}
}
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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