Theory and Security of Voting Systems (TSVS, SoSe 2026)

Lecture 2 hours, Kirsten; exercises 2 hours, Kirsten

For BSc students, the course is officially called "Theory and Security of Voting Systems for Bachelor".

Overview

Voting is an important part of democratic societies and potentially has a broad impact. Yet, with or without the use of modern technology, voting is full of algorithmic and security challenges, and the failure to address these challenges in a controlled manner may produce fundamental flaws in the voting system and potentially undermine critical societal aspects.

In this lecture, we discuss voting systems from various perspectives, notably social choice theory, security, and cryptography. What should a voting system fulfill? When is a voting system secure, even independent of the involved software? Which mechanisms should be investigated for that matter? Which methods are suitable to address these challenges?

We will investigate cryptographic voting systems, algorithmic tallying procedures, statistical methods to test the reliability of an election result, and distinguish the different layers of a voting system.

Preliminary Knowledge

Foundations on cryptography and security, as taught, for instance, in the lecture IT-Sicherheit, are recommended. Moreover, we make an effort to coordinate the cryptography parts of the lecture with the practical "Cryptography" that you can optionally take in parallel.

Organization

• 2+2 hours per week

• Lecturer: Dr. Michael Kirsten

• Teaching assistant: Dr. Michael Kirsten

Please register for the Moodle course.

Events

Curriculum

This lecture currently covers the three sections of voting theory with seven individual lectures, cryptographic voting with six individual lectures, and post-election audits with two individual lectures.

Voting Theory

1. Introduction with selected voting rules and paradoxes
2. Classical characterizations and impossibilities
3. Condorcet extensions and multi-round rules
4. Strategyproofness and multiple elections
5. Seat apportionment methods and divisor methods
6. Approval-based committee voting
7. Preference-based multiwinner voting and voting games

Cryptographic Voting

1. Introduction with objective, attacker models, and trust assumptions
2. Cryptographic foundations and primitives
3. Paper-based secure voting systems
4. Computer-based secure voting systems
5. The Swiss Post voting system
6. Code voting, revoting, everlasting privacy, and secure ranked voting

Post-Election Audits

1. Introduction, properties, and betting analogy
2. Comparison audits and audits for advanced voting systems

Authors and Acknowledgment

The lecture material (available via the Moodle course) is collected and maintained by Michael Kirsten, but reassembles slides that are originally created by Ulle Endriss (University of Amsterdam), Piotr Skowron (University of Warsaw), Lirong Xia (Rutgers University), Jörg Rothe (Heinrich Heine University Düsseldorf), Ariel Procaccia (Carnegie Mellon University), Friedrich Pukelsheim (University of Augsburg), Tomáš Kroupa (Czech Technical University in Prague), Felix Dörre (Karlsruhe Institute of Technology), Florian Moser (famoser GmbH/INRIA Nancy), and Philip B. Stark (University of California, Berkeley), and further contains slides that are based on lecture notes originally created by Bernhard Löwe, Carmen Kempka, Ferdinand Sauer, Rebecca Schwerdt, and Felix Dörre (all at Karlsruhe Institute of Technology). All this material has either been made publicly available or provided directly by the courtesy of the authors.

Exams

A written examination at the end of the semester will test your understanding. The examination will be on paper and closed book. Basic or scientific calculators will be permitted, however these are not allowed and may be considered as attempted cheating if they are programmable, can store notes, connect to the internet, or have any communication features. Nevertheless, the exam questions will also be solvable without the use of electronic calculators if you can do basic additions, subtractions, multiplications, divisions, exponentiations, or square roots, e.g., on paper. You will be given 120 minutes to complete the exam. Registration is mandatory and via the LSF system.

The regular examination takes place on Monday, 3 August 2026 from 10:30 a.m. to roughly 12:30 in the building at Theresienstraße 41 in room C 123. Registration is possible from Sunday, 28 June until Sunday, 12 July. If you need some adjustments to compensate for disabilities or impairments, please contact the lecturer until Wednesday, 22 July.

The retake examination takes place on Monday, 21 September 2026 from 14:00 to roughly 16:00 in the building at Butenandtstraße 13 in room F 0.001. Registration is possible from Monday, 31 August until Sunday, 13 September. If you need some adjustments to compensate for disabilities or impairments, please contact the lecturer until Wednesday, 16 September.