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Carl Magnus Bruhner

PhD student

I’m a PhD student in computer science & cybersecurity. I study Internet security and privacy through large-scale measurements of the web PKI, focusing on certificates, trust, and real-world usage.

Research for a more secure and privacy-preserving Internet

I am a PhD student in computer science and cybersecurity, funded by and part of the Wallenberg AI, Autonomous Systems and Software Program (WASP) graduate school. Under the supervision of Professor Niklas Carlsson and as part of the Security and Networks Group, my research investigates Internet security and privacy with a focus on the Web Public Key Infrastructure (Web PKI).

My work examines how digital certificates are issued, managed, and revoked, and how these processes align—or fail to align—with standards, policies, and security expectations. Using Internet measurement methods, I study certificate usage “in the wild” to identify misconfigurations, bottlenecks, and systemic weaknesses. This empirical approach not only uncovers trends and risks in today’s deployment but also highlights opportunities for improving trust models, operational practices, and Web PKI ecosystem governance.

I enjoy engaging with the wider internet measurement and security research communities and have served on the MADWeb 2025 program committee as well as the IMC Shadow TPC 2025 (—and am open to more opportunities!).

Beyond research, I am passionate about teaching and mentoring. I also serve as a PhD student representative on a number of the university’s boards.

I welcome collaborations with researchers, students, and industry partners who share an interest in building a more secure and privacy-preserving Internet—or a more cybersecure world in general!

Background and assignments in short

Education

  • PhD in Computer Science, LiU (2023–)
  • Information Technology, M.Sc. in Engineering (Civilingenjör), Secure Systems profile, LiU (2022)
  • B.Sc. with a major in Business Administration (Civilekonom), LiU (2021)

 

Assignments

Publications

2024

Marcus Döberl, York Freiherr von Wangenheim, Carl Magnus Bruhner, David Hasselquist, Martin Arlitt, Niklas Carlsson (2024) Chain-Sawing: A Longitudinal Analysis of Certificate Chains Proc. IFIP Networking 2024, p. 122-130 (Conference paper) Continue to DOI
David Cerenius, Martin Kaller, Carl Magnus Bruhner, Martin Arlitt, Niklas Carlsson (2024) Trust Issue(r)s: Certificate Revocation and Replacement Practices in the Wild Passive and Active Measurement: 25th International Conference, PAM 2024. Virtual Event, March 11–13, 2024. Proceedings, Part II., p. 293-321 (Conference paper) Continue to DOI
Carl Magnus Bruhner, Oscar Linnarsson, Matus Nemec, Martin Arlitt, Niklas Carlsson (2024) Monogamous relationships with short-term commitment are the best (for certificate management)

2023

Carl Magnus Bruhner, David Hasselquist, Niklas Carlsson (2023) Bridging the Privacy Gap: Enhanced User Consent Mechanisms on the Web Proc. NDSS Workshop on Measurements, Attacks, and Defenses for the Web (MADWeb @NDSS) (Conference paper) Continue to DOI

2022

Carl Magnus Bruhner, Oscar Linnarsson, Matus Nemec, Martin Arlitt, Niklas Carlsson (2022) Changing of the Guards: Certificate and Public Key Management on the Internet Passive and active measurement (PAM 2022), p. 50-80 (Conference paper) Continue to DOI

Research

Teaching

Supervision and lecturing

I support projects and co-supervise theses for students in the Information Technology, M.Sc. in Engineering program (TDDE35 Secure Systems: Project Semester including Bachelor Thesis Project). Additionally, I supervise Master’s theses (TQxx30/33), primarily for the M.Sc. in Engineering programs.

Since spring 2025, I am a lecturer in the course TDTS04 Computer Networks and Distributed Systems, with responsibility of the part on distributed systems.

Cybersecurity, Master's Programme, 120 credits

Help defend society against cyberattacks and develop next-generation security solutions. This programme combines theoretical courses and practical exercises which will give you tools to address the digital security challenges of today and tomorrow.

About the division

Colleagues at ADIT

About the department