When Cryptography Meets Reality: Insights from the Swiss Post E-Voting Protocol

How do cryptography and real-world constraints meet in an e-voting system? Electronic voting has been back in production in Switzerland since 2023. Starting from the basics, this talk presents the cryptographic protocol underlying the Swiss Post e-voting system, the voter journey, and the associated trust assumptions. Emphasis is placed on the trade-offs between the system's security properties, usability, and performance. Measures taken to strengthen transparency and auditability are also described.
The first focus of the talk is the e-voting protocol currently deployed by some Swiss cantons, enabling citizens to securely cast their votes online in legally binding elections. We then move from the present to the near future, detailing the new protocol under development and highlighting how it is expected to further strengthen both the security and the verifiability of the system.
Throughout the talk, we keep a close eye on practical constraints: how the Federal Ordinance on electronic voting shapes trust assumptions and transparency requirements, and how operational procedures influence the generation of election parameters and the verification of protocol steps. We also show how these requirements affect system design choices, deployment procedures, and the practical interpretation of security guarantees. We also address usability and accessibility, discussing how the voting process can become understandable and verifiable for all voters. The talk concludes with open challenges and ongoing work on distributing trust between the system components.