François Dupressoir
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François Dupressoir
@francois.dupressoir.eu
95 followers 57 following 55 posts
Proof nerd, dad, computer scientist.
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francois.dupressoir.eu
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lambdafu.bsky.social Marcus Brinkmann @lambdafu.bsky.social · Oct 5
This is a friendly reminder that the call for contributed talks to Real World Crypto in Taipei 2026 is open until October 10. We are looking for interesting talks bridging cryptography and its real-world use! Also it’s a great way to meet new people! rwc.iacr.org/2026/contrib...
RWC 2026 call for papers
Real World Crypto Symposium
rwc.iacr.org
October 5, 2025 at 7:14 PM
Reposted by François Dupressoir
eprint.ing.bot
Faster Verification of Faster Implementations: Combining Deductive and Circuit-Based Reasoning in EasyCrypt (José Bacelar Almeida et al.) ia.cr/2025/1607
Abstract. We propose a hybrid formal verification approach that combines high-level deductive reasoning and circuit-based reasoning and apply it to highly optimized cryptographic assembly code. Our approach permits scaling up formal verifi- cation in two complementary directions: 1) it reduces the proof effort required for low-level functions where the computation logics are obfuscated by the intricate use of architecture-specific instructions and 2) it permits amortizing the effort of proving one implementation by using equivalence checking to propagate the guarantees to other implementations of the same computation using different optimizations or targeting different architectures. We demonstrate our approach via an extension to the EasyCrypt proof assistant and by revisiting formally verified implementations of ML-KEM in Jasmin. As a result, we obtain the first formally verified implementation of ML-KEM that offers performance comparable to the fastest non-verified implementation in x86-64 architectures.
September 11, 2025 at 4:14 PM
Reposted by François Dupressoir
eprint.ing.bot
Threshold Signatures Reloaded: ML-DSA and Enhanced Raccoon with Identifiable Aborts (Giacomo Borin, Sofía Celi, Rafael del Pino, Thomas Espitau, Guilhem Niot, Thomas Prest) ia.cr/2025/1166
Abstract. Threshold signatures enable multiple participants to collaboratively produce a digital signature, ensuring both fault tolerance and decentralization. As we transition to the post-quantum era, lattice-based threshold constructions have emerged as promising candidates. However, existing approaches often struggle to scale efficiently, lack robustness guarantees, or are incompatible with standard schemes — most notably, the NIST-standard ML-DSA. In this work, we explore the design space of Fiat-Shamir-based lattice threshold signatures and introduce the two most practical schemes to date. First, we present an enhanced TRaccoon-based [DKM+24] construction that supports up to 64 participants with identifiable aborts, leveraging novel short secret-sharing techniques to achieve greater scalability than previous state-of-the-art methods. Second — and most importantly — we propose the first practical ML-DSA-compatible threshold signature scheme, supporting up to 6 users. We provide full implementations and benchmarks of our schemes, demonstrating their practicality and efficiency for real-world deployment as protocol messages are computed in at most a few milliseconds, and communication cost ranges from 10.5 kB to 525 kB depending on the threshold. Image showing part 2 of abstract.
June 20, 2025 at 9:11 PM
Reposted by François Dupressoir
malb.bsky.social
Come work with the rather excellent @bedow.bsky.social (and also me)
bedow.bsky.social Benjamin Dowling @bedow.bsky.social · Jan 10
Excited to announce a funded PhD position analysing the Social Foundations of Cryptography here at King's College London with me and @malb.bsky.social . Applications open now, feel free to reach out for a chat.

social-foundations-of-cryptography.gitlab.io

Link in next post!
Social Foundations of Cryptography · An EPSRC funded research project grounding cryptographic notions in ethnographic findings.
social-foundations-of-cryptography.gitlab.io
January 10, 2025 at 5:49 PM
Reposted by François Dupressoir
eprint.ing.bot
Parametrizing Maximal Orders Along Supersingular ℓ-Isogeny Paths (Laia Amorós, James Clements, Chloe Martindale) ia.cr/2025/033
Abstract. Suppose you have a supersingular ℓ-isogeny graph with vertices given by j-invariants defined over 𝔽_(p²), where p = 4 ⋅ f ⋅ ℓ^(e) − 1 and ℓ ≡ 3 (mod  4). We give an explicit parametrization of the maximal orders in B_(p, ∞) appearing as endomorphism rings of the elliptic curves in this graph that are  ≤ e steps away from a root vertex with j-invariant 1728. This is the first explicit parametrization of this kind and we believe it will be an aid in better understanding the structure of supersingular ℓ-isogeny graphs that are widely used in cryptography. Our method makes use of the inherent directions in the supersingular isogeny graph induced via Bruhat-Tits trees, as studied in [1]. We also discuss how in future work other interesting use cases, such as ℓ = 2, could benefit from the same methodology.
January 9, 2025 at 3:04 PM
Reposted by François Dupressoir
malb.bsky.social
Khanh and Eamonn are organising UK Crypto Day on 20 February at King's College London.

Registration is free (and open) but required: uk-crypto-day.github.io/2025/02/20/u...

Help us spread the word and see you there.
UK Crypto Day: 20 February 2025
Schedule
uk-crypto-day.github.io
January 3, 2025 at 10:56 AM
francois.dupressoir.eu
The ProTeCS 2025 call for presentations is out. (Short) Submissions by February 20, 2025.

Then off to Madrid just before EuroCrypt to present your nerdy results. (May 3.)

Proof nerds: shape the community, and submit the kind of work you want to hear about!

protecs-workshop.gitlab.io/call
Call for Presentations
Workshop on Proofs and Proof Techniques for Cryptographic Security. Affiliated with Eurocrypt 2025.
protecs-workshop.gitlab.io
November 26, 2024 at 8:00 PM
Reposted by François Dupressoir
durumcrustulum.com
The EasyCrypt proofs for X-Wing are now on GitHub: github.com/formosa-cryp...
GitHub - formosa-crypto/formosa-x-wing
Contribute to formosa-crypto/formosa-x-wing development by creating an account on GitHub.
github.com
October 30, 2024 at 10:12 PM
Reposted by François Dupressoir
rwc.iacr.org
Stipend applications for #RealWorldCrypto2025 are now open! These grants support students, early-career researchers, and individuals from underrepresented groups, enabling them to engage with pivotal developments in cryptographic research and applications.

rwc.iacr.org/2025/stipend...
RWC 2025 student stipends
Real World Crypto Symposium
rwc.iacr.org
October 28, 2024 at 3:41 PM
Reposted by François Dupressoir
malb.bsky.social
My department is recruiting two lecturers (~ assistant professors) www.kcl.ac.uk/jobs/096025-... Cryptography is not high on the list of priorities for these ones, though.
Lecturer in Computer Science x2
www.kcl.ac.uk
October 4, 2024 at 1:21 PM
francois.dupressoir.eu
The Rumineers
onlymemes.bsky.social OnlyMemes @onlymemes.bsky.social · Oct 1
Name this band
In a foggy pasture with leaf-less trees in the background stand from left to right, a white llama, a tan and black sheep, a brown bull cow with a shaggy mane, a white and brown goat, and then a black and white speckled rooster in front of the cow. They are all staring moodily at you.
October 1, 2024 at 7:43 PM
Reposted by François Dupressoir
cryspen.com
We are happy to announce the release of OpenMLS v0.6, a significant update to our open-source MLS implementation. This version includes several new features and improvements.

Read all details on the blog: https://buff.ly/47aL5dz

#MLS #opensource #cryptography
OpenMLS 0.6 released
Today, we are releasing version 0.6 of OpenMLS. In this post we’ll go over the most significant changes since our last release. New Storage Provider To make it easier to persist group state, the…
buff.ly
September 4, 2024 at 3:32 PM
Reposted by François Dupressoir
clist.bsky.social
We are hiring a postdoc at LMU's Munich Center for Mathematical Philosophy. Areas: decision theory, social choice theory, philosophy of action, the study of agency & free will, and/or related themes in the philosophy of mind. Deadline 8 Sept. Please spread the word. job-portal.lmu.de/jobposting/4...
Postdoctoral Fellow (m/f/x)
job-portal.lmu.de
August 5, 2024 at 5:21 PM
Reposted by François Dupressoir
malb.bsky.social
At @SandboxAQ we're hiring for an engineering consulting position in the areas of (post-quantum) cryptography or privacy: www.iacr.org/jobs/item/3716 part-time or full-time.
Engineering Consulting Position
www.iacr.org
June 21, 2024 at 7:15 PM
Reposted by François Dupressoir
malb.bsky.social
Postdoc Position in Cryptography: Social Foundations of Cryptography: martinralbrecht.wordpress.com/2024/06/11/c...

Se also: social-foundations-of-cryptography.gitlab.io
Cryptography Postdoc Position in Social Foundations of Cryptography
We are looking for a postdoc to work with us on the social foundations of cryptography. This is a two-year full-time position based in London at a salary of £47,978 per annum. We. This postdoc positio...
martinralbrecht.wordpress.com
June 12, 2024 at 10:47 AM
Reposted by François Dupressoir
eprint.ing.bot
A Tight Security Proof for SPHINCS⁺, Formally Verified (Manuel Barbosa, François Dupressoir, Andreas Hülsing, Matthias Meijers, Pierre-Yves Strub) ia.cr/2024/910
Abstract. SPHINCS⁺ is a post-quantum signature scheme that, at the time of writing, is being standardized as SLH-DSA. It is the most conservative option for post-quantum signatures, but the original tight proofs of security were flawed—as reported by Kudinov, Kiktenko and Fedorov in 2020. In this work, we formally prove a tight security bound for SPHINCS⁺ using the EasyCrypt proof assistant, establishing greater confidence in the general security of the scheme and that of the parameter sets considered for standardization. To this end, we reconstruct the tight security proof presented by Hülsing and Kudinov (in 2022) in a modular way. A small but important part of this effort involves a complex argument relating four different games at once, of a form not yet formalized in EasyCrypt (to the best of our knowledge). We describe our approach to overcoming this major challenge, and develop a general formal verification technique aimed at this type of reasoning. Enhancing the set of reusable EasyCrypt artifacts previously produced in the formal verification of stateful hash-based cryptographic constructions, we (1) improve and extend the existing libraries for hash functions and (2) develop new libraries for fundamental concepts related to hash-based cryptographic constructions, including Merkle trees. These enhancements, along with the formal verification technique we develop, further ease future formal verification endeavors in EasyCrypt, especially those concerning hash-based cryptographic constructions. Image showing part 2 of abstract.
June 8, 2024 at 6:09 AM
francois.dupressoir.eu
The University of Bristol is looking to grow its verification activities. A lectureship in verification is open in an adjacent group. The group itself is very project-driven, with the environment around it giving a nice mix of curiosity- and mission-driven groups.

www.bristol.ac.uk/jobs/find/de...
Details | Working at Bristol | University of Bristol
www.bristol.ac.uk
June 1, 2024 at 10:24 AM
Reposted by François Dupressoir
malb.bsky.social
We are looking for a postdoc to work with us on lattice-based cryptography: www.kcl.ac.uk/jobs/090126-...

Stuff like e.g. this malb.io/sis-with-hin...

Funded by this grant: martinralbrecht.wordpress.com/2023/01/31/e...
Research Fellow/Research Associate in Cryptography
www.kcl.ac.uk
May 28, 2024 at 8:14 AM
Reposted by François Dupressoir
eprint.ing.bot
Formally verifying Kyber Episode V: Machine-checked IND-CCA security and correctness of ML-KEM in EasyCrypt (José Bacelar Almeida et al.) ia.cr/2024/843
Abstract. We present a formally verified proof of the correctness and IND-CCA security of ML-KEM, the Kyber-based Key Encapsulation Mechanism (KEM) undergoing standardization by NIST. The proof is machine-checked in EasyCrypt and it includes: 1) A formalization of the correctness (decryption failure probability) and IND-CPA security of the Kyber base public-key encryption scheme, following Bos et al. at Euro S&P 2018; 2) A formalization of the relevant variant of the Fujisaki-Okamoto transform in the Random Oracle Model (ROM), which follows closely (but not exactly) Hofheinz, Hovelmanns and Kiltz at TCC 2017; 3) A proof that the IND-CCA security of the ML-KEM specification and its correctness as a KEM follows from the previous results; 4) Two formally verified implementations of ML-KEM written in Jasmin that are provably constant-time, functionally equivalent to the ML-KEM specification and, for this reason, inherit the provable security guarantees established in the previous points. The top-level theorems give self-contained concrete bounds for the correctness and security of MLKEM down to (a variant of) Module-LWE. We discuss how they are built modularly by leveraging various EasyCrypt features. Image showing part 2 of abstract.
May 31, 2024 at 8:32 AM
Reposted by François Dupressoir
eprint.ing.bot
SQIsign2D-West: The Fast, the Small, and the Safer (Andrea Basso, Luca De Feo, Pierrick Dartois, Antonin Leroux, Luciano Maino, Giacomo Pope, Damien Robert, Benjamin Wesolowski) ia.cr/2024/760
Abstract. We introduce SQIsign2D-West, a variant of SQIsign using two-dimensional isogeny representations. SQIsignHD was the first variant of SQIsign to use higher dimensional isogeny representations. Its eight-dimensional variant is geared towards provable security but is deemed unpractical. Its four-dimensional variant is geared towards efficiency and has significantly faster signing times than SQIsign, but slower verification owing to the complexity of the four-dimensional representation. Its authors commented on the apparent difficulty of getting any improvement over SQIsign by using two-dimensional representations. In this work, we introduce new algorithmic tools that make two-dimensional representations a viable alternative. These lead to a signature scheme with sizes comparable to SQIsignHD, slightly slower signing than SQIsignHD but still much faster than SQIsign, and the fastest verification of any known variant of SQIsign. We achieve this without compromising on the security proof: the assumptions behind SQIsign2D-West are similar to those of the eight-dimensional variant of SQIsignHD. Additionally, like SQIsignHD, SQIsign2D-West favourably scales to high levels of security Concretely, for NIST level I we achieve signing times of 80 ms and verifying times of 4.5 ms, using optimised arithmetic based on intrinsics available to the Ice Lake architecture. For NIST level V, we achieve 470 ms for signing and 31 ms for verifying. Image showing part 2 of abstract.
May 20, 2024 at 3:35 AM
Reposted by François Dupressoir
malb.bsky.social
UK Crypto Day | 20 June 2024 | Edinburgh

uk-crypto-day.github.io/2024/06/20/u...
UK Crypto Day: 20 June 2024 at The University of Edinburgh
Schedule
uk-crypto-day.github.io
April 24, 2024 at 7:45 PM