Lena Heimberger

About

Hi! I'm a PhD student broadly working on privacy-preserving post-quantum protocols, especially OPRFs and lately anonymous credentials. As a side quest, I also work on key transparency. I'm based at the Institute of Information Security at the University of Technology in Graz, working under the supervision of Christian Rechberger.

News

• The slides from my talk about deployed OPRFs at real-world MPC in Taipei are available here.

Publications

1. Leap: A Fast, Lattice-based OPRF with Application to Private Set Intersection
   Lena Heimberger, Daniel Kales , Riccardo Lolato, Omid Mir, Sebastian Ramacher, Christian Rechberger (Eurocrypt, 2025)
   paper eprint presentation conference artifact (Results Reproduced) github repository
2. BISON: Blind Identification with Stateless scOped pseudoNyms
   Jakob Heher, Stefan More, Lena Heimberger(AsiaCCS, 2025)
   arxiv
3. Private SCT Auditing, Revisited
   Lena Heimberger, Christopher Patton, Bas Westerbaan (preprint, 2025)
   eprint
4. OPRFs from Isogenies: Designs and Analysis
   Lena Heimberger, Tobias Hennerbichler, Fredrik Meisingseth, Sebastian Ramacher, Christian Rechberger (AsiaCCS, 2024)
   eprint github repository slides blog post

External Blogposts, Talks, Tables...

• RWMPC 2026: OPRFs in the Wild: A Survey of Real-World Deployments
• Paris Crypto Days 2026: Oblivious Pseudorandom Functions in a Post-Quantum World
• Cloudflare 2025, I: Chris Patton and I looked at the state of the art post-quantum anonymous credentials.
• Cloudflare 2025, II: I also worked on private rate limiting. I presented our approach for stateful, revocable anonymous credentials at IETF 124 with Thibault Meunier.
• SCT auditing was the main focus point of my internship at Cloudflare in 2024. Together with recent developments in Private Information Retrieval and transparency log design, we are getting closer to wide-scale SCT auditing. I presented a part of our work the transparency.dev summit in 2024. Check out the slides and the talk recording (on youtube).
• The big table of post-quantum friendly OPRFs, which is an ongoing project collecting all post-quantum friendly OPRFs in a single table.
• Lecture notes on lattices that I compiled as a part of the Mathematical Foundations in Cryptography class at Graz University of Technology. Lattices have since been removed from the class, so I host the notes here instead.
• SPHINCS+ implementation in Java, done as a part of an internship at the Insitute of Applied Information and Communication Security in Graz, Austria
  
• Lattice-ZK, the master project of my student Florian Lugstein, implementing the zero-knowledge range proof system Lantern in SAGE. Aside from being the first implementation of the scheme, he took care to explain every step necessary. This makes it a good introduction to lattice-based zero-knowlege proofs and lattice cryptography in general. You can also try out an interactive version hosted on Binder (may take a while to load)!
  

Contact

• University Page
  
• Institute Page
  
• Email: given name dot last name ät tugraz dot at
• Github
  

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