*Date and Location* 27 April 2026, 11:00 -- 12:00 (Attention: Starting time is **:00**) Universität Bern, Hauptgebäude, Hochschulstrasse 4, Room 206.

*Speaker* Prof. ‪Stefano Tessaro University of Washington

*Title* Practice-Driven Theoretical Cryptography

*Abstract* A large fraction of modern academic cryptography is organised around designing primitives and protocols that admit proofs of security within carefully specified formal models and under well-founded assumptions. Yet many of the mechanisms that underpin today’s digital infrastructure were either not developed with these proof frameworks in mind or benefit only from partial validation within them.

In this talk, I will explain how filling this gap gives rise to a practice-driven theoretical agenda aimed at establishing the strongest possible security guarantees for cryptographic mechanisms that are already deployed or being standardised, without redesigning them to fit current proof frameworks. I will illustrate how this perspective often leads to new theoretical questions of broader appeal, including connections to theoretical computer science more broadly. I will present several vignettes from our recent work, including research motivated by standardization efforts in privacy-preserving authentication and distributed cryptography, as well as an ongoing multi-year program aimed at understanding the security of block cipher design paradigms – the foundations of modern symmetric-key encryption standards – through connections to fundamental questions about randomness and structure.

*Brief bio* Stefano Tessaro is a Professor in the Paul G. Allen School of Computer Science & Engineering at the University of Washington and is currently a Visiting Professor at ETH Zurich. He works primarily on cryptography, computer security and theoretical computer science. Earlier, he was an assistant professor at UC Santa Barbara, where he held the Glen and Susanne Culler Chair. He received a PhD from ETH Zurich in 2010 and held postdoctoral appointments at UC San Diego and MIT. He has received several awards for his work, including a Sloan Research Fellowship, an NSF CAREER Award, a Hellman Fellowship and a Best Paper Award at EUROCRYPT 2017.

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See you there!

Christian Cachin

--- Christian Cachin email: christian.cachin@unibe.ch Cryptology and Data Security Group web: crypto.unibe.ch/cc Institute of Computer Science tel: +41 31 684 8560 University of Bern Neubrückstrasse 10, CH-3012 Bern, Switzerland