Research Visit and Seminar Talks @ INRIA Bordeaux

19 December 2025

In November 2025, two researchers from the QuSAC lab, Marzio Mula and Sebastian Spindler, visited the CANARI project-team at Inria Bordeaux and the Institut de Mathématiques de Bordeaux. During their stay, they gave two seminar talks at the Algorithmic Number Theory Seminar (Séminaire de Théorie Algorithmique des Nombres).

In his talk “Modular polynomial-based proofs of knowledge for isogeny paths” (joint work with the QuSAC group and CODE colleague S. Kleine), Sebastian explained how the individual steps in an isogeny path can be encoded via suitable modular polynomials and turned into rank-1 constraint systems for zero-knowledge proof systems. He highlighted how using canonical, Atkin, and Weber modular polynomials leads to smaller and more efficient proofs compared to the classical modular polynomial.

Marzio presented “Dynamics of the Hessian transformation” (joint work with E. Broggini, M. Houben, D. Lazzarini, R. Lolato, F. Pintore, and D. Taufer), focusing on dynamical systems arising from the Hessian of ternary cubics and binary quartics on the modular curve X(1). He discussed how these maps arise from suitable group homomorphisms, leading to remarkably symmetric functional graphs.

The visit to the CANARI team offered a valuable opportunity to present ongoing QuSAC research on isogeny-based cryptography and arithmetic dynamics, exchange ideas with local experts, and explore new directions for collaboration.

Aktuelles

Asiacrypt 2025

From the 8th until the 12th of December, members of the QuSAC group visited Asiacrypt, the largest cryptography conference of Asia. The 2025 edition took place in Melbourne, Australia. It was a valuable opportunity to speak with other researches and learn about recent research. In total, 3 papers accepted at the conference were (co-)authored by members of the QuSAC group.

Swissogeny Day Lausanne

On November 26th Shernyce Duncombe, Marzio Mula and Sebastian Spindler participated in the fourth edition of the Swissogeny Day, which was hosted at the EPFL in Lausanne. The one-day workshop kicked off with research talks on generalized lollipop attacks, an alternative approach to SQIsign incorporating level structures, and an attack on the active security of PEARL-SCALLOP.

Invited Speaker at the Australian Summer School on Privacy 2025

Prof. Daniel Slamanig was an invited speaker at the Australian Summer School on Privacy 2025, held at the University of New South Wales (UNSW) in Sydney and organized by Prof. Sushmita Ruj and Prof. Salil Kanhere. The summer school brought together students, researchers, and practitioners from academia and industry to explore current developments in privacy-enhancing technologies, including topics such as cryptography for privacy, differential privacy, usable privacy, and AI privacy.

Talk @ Crypto 2025

On August 18th, Sebastian Spindler presented the paper “More Efficient Isogeny Proofs of Knowledge via Canonical Modular Polynomials”, which arose from a collaboration between the QuSAC group and CODE colleague Sören Kleine, remotely during the 45th edition of the CRYPTO conference.

Isogeny Club

On October 7th, Sebastian Spindler gave the online talk “Counting ℓ-isogenies with different modular polynomials” as part of the seventh season of the Isogeny Club. The talk covered both the CRYPTO paper “More Efficient Isogeny Proofs of Knowledge via Canonical Modular Polynomials”, which is a joint work of the QuSAC group and CODE colleague Sören Kleine, as well as subsequent, not yet published follow-up work that investigates other modular polynomials.

Crypto Day

On September 25th and 26th, Sebastian Spindler participated in the 39th Crypto Day, which was hosted by the genua GmbH in Kirchheim near Munich. At the event, Sebastian had the opportunity to converse with researchers from other universities and from the industry mainly about practical aspects of cryptography. Additionally, in his talk “Isogeny Proofs of Knowledge – A Survey” Sebastian gave an overview over the evolution of proofs of knowledge for isogeny paths over the last two years.