Shai Levin — Cryptographic Protocols Research

This site serves as a repository for some of my projects. You can contact me via shai(at)science(dot)capetown.

About Me

Born and raised in South Africa, currently living in Gothenburg, Sweden. After living in New Zealand for 9 years, I completed my PhD in Cryptography at University of Auckland in 2025 under Steven Galbraith. I love Muay Thai, the national martial art of Thailand. I am undefeated with 9 wins, winning a New Zealand (NZMAF) super-cruiserweight (86kg) title in my last fight.

I am primarily interested in constructing practical, provably secure authentication and privacy-preserving protocols; both in the post-quantum (isogeny and code-based) and classical (discrete-log and pairing-based) settings. My primary focus in my PhD thesis has been applying modern, succinct generic proof systems (zk-SNARKs) as a building block for efficient post-quantum protocols, such as verifiable random functions, signature schemes and more. Currently I am interested in constructing protocols for use in anonymous credential systems (e.g. device-binding, unlinkability and post-quantum security).

I am currently working as a postdoctoral researcher at Chalmers University of Technology in Gothenburg, Sweden, supervised by Elena Pagnin.

My PhD Thesis

I successfully defended my thesis in December 2025, passing with no revisions required. It is available here: Constructing Secure Protocols from Proofs of Knowledge and Isogenies.

Publications

(Submitted to S&P '27): Device Binding for Anonymous Credentials on Legacy Phones with Sofía Celi, Anja Lehmann and Alexandros Zacharakis.
(Submitted to Asiacrypt '26): SPRINT: New Isogeny Proofs of Knowledge and Isogeny-Based Signatures with Thomas Den Hollander, Marzio Mula, Robi Pedersen, Daniel Slamanig and Sebastian Spindler.
A Note on Zero-Knowledge Simulator of the CROSS Identification Protocol — authored solo.
(Submitted to Mathematical Cryptology): Further Connections Between Isogenies of Supersingular Curves and Bruhat-Tits Trees with Steven Galbraith, Valerie Gilchrist and Ari Markowitz.
(Asiacrypt 2025): Faster Proofs and VRFs from Isogenies with Robi Pedersen.
(IACR CiC Vol. 1, Issue 4): A Key-Recovery Attack on a Leaky Seasign Variant — authored solo.
(Africacrypt 2024): CDLS: Proving Knowledge of Committed Discrete Logarithms with Soundness with Sofía Celi and Joe Rowell during an internship at Brave.
(ACNS 2023): Efficient Isogeny Proofs Using Generic Techniques with Kelong Cong and Yi-Fu Lai.

Miscellaneous Projects

Code for generating the supersingular isogeny graph, since it is very hard to find an implementation that works in the "correct" way.
A (now insecure) implementation of Supersingular Isogeny Key Exchange (SIKE) in Python.
Slides for a talk I've done on Expander Graphs in Cryptography.
My honours project with a summary of Elliptic Curves, their isogenies, and a way to construct lifts from isogeny graphs.
My slides for a "thesis in three" on my honours project.
A report on an open problem of existence of particular Ramanujan graphs.
Cyber-security reports done during my undergrad on wireless network security, applications of VPNs and the vulnerability of cheap IoT devices.
I maintained this website.