Homepage of Karen AzariI am an assistant professor at University of Vienna and member of the research group Theory and Applications of Algorithms at the faculty of computer science. My area of research is cryptography and I specialize in formal security definitions and security proofs of cryptographic protocols. In particular, I work on secure group messaging, proof systems for decentralized systems and (foundations of) resource-restricted cryptography, and am always curious to explore new areas of cryptography.
My academic background is in mathematics. I did my PhD studies at the Institute of Science an Technology Austria (ISTA), where I was fortunate to be advised by Krzysztof Pietrzak. After that I moved to ETH Zurich, where I gained very valuable experience in teaching and great advice by Dennis Hofheinz.
If you are interested in pursuing PhD studies in my group, please reach out to me.
News
Security Amplification of Threshold Signatures in the Standard Model, joint work with Cecilia Boschini, Kristina Hostáková and Michael Reichle, was accepted at TCC 2025.
Tighter provable security for TreeKEM, joint work with Andreas Ellison, was accepted at ACNS 2025 and won the Best Student Paper award.
Securely Instantiating Half Gates Garbling in the Standard Model, joint work with Anasuya Acharya, Mirza Ahad Baig, Dennis Hofheinz and Chethan Kamath, was accepted at PKC 2025.
On the Adaptive Security of Free-XOR-based Garbling Schemes in the Plain Model, joint work with Anasuya Acharya and Chethan Kamath, was accepted at EUROCRYPT 2025.
Teaching
Spring semester 2025:
Team
Maximilian von Consbruch (PhD studies 2025 – today)
Scientific service
I was a member of the following program committees:
- CFAIL 2025, ASIACRYPT 2024, CFAIL 2024, CRYPTO 2024, EUROCRYPT 2023, TCC 2022
Publications
- Karen Azari, Cecilia Boschini, Kristina Hostáková, Michael Reichle. Security Amplification of Threshold Signatures in the Standard Model. TCC 2025. [Full Version]
- Karen Azari, Andreas Ellison. Tighter provable security for TreeKEM. ACNS 2025. [Full Version]
- Anasuya Acharya, Karen Azari, Mirza Ahad Baig, Dennis Hofheinz and Chethan Kamath. Securely Instantiating Half Gates Garbling in the Standard Model. PKC 2025. [Full Version]
- Anasuya Acharya, Karen Azari and Chethan Kamath. On the Adaptive Security of Free-XOR-based Garbling Schemes in the Plain Model. EUROCRYPT 2025. [Full Version]
- Joel Alwen, Benedikt Auerbach, Miguel Cueto Noval, Karen Klein, Guillermo Pascual-Perez and Krzysztof Pietrzak. DeCAF: Decentralizable Continuous Group Key Agreement with Fast Healing. SCN 2024. [Full Version]
- Dennis Hofheinz, Kristina Hostáková, Julia Kastner, Karen Klein, and Akin Ünal. Compact Lossy Trapdoor Functions and Selective Opening Security From LWE. PKC 2024. [Full Version]
- Dennis Hofheinz, Julia Kastner, and Karen Klein. The Power of Undirected Rewindings for Adaptive Security. CRYPTO 2023. [Full Version]
- Hamza Abusalah, Peter Gaži, Georg Fuchsbauer, and Karen Klein. SNACKs: Leveraging Proofs of Sequential Work for Blockchain Light Clients. ASIACRYPT 2022. [Full Version]
- Charlotte Hoffmann, Pavel Hubáček, Chethan Kamath, Karen Klein, and Krzysztof Pietrzak. Practical Statistically-Sound Proofs of Exponentiation in Any Group. CRYPTO 2022. [Full Version]
- Joel Alwen, Benedikt Auerbach, Miguel Cueto-Noval, Karen Klein, Guillermo Pascual-Perez, Krzysztof Pietrzak, and Michael Walter. CoCoA: Concurrent Continuous Group Key Agreement. EUROCRYPT 2022. [Full Version]
- Chethan Kamath, Karen Klein, Krzysztof Pietrzak, and Michael Walter. The cost of adaptivity in security games on graphs. TCC 2021. [Full Version]
- Chethan Kamath, Karen Klein, and Krzysztof Pietrzak. On treewidth, separators and Yao’s garbling. TCC 2021. [Full Version]
- Joel Alwen, Benedikt Auerbach, Mirza Ahad Baig, Miguel Cueto, Karen Klein, Guillermo Pascual-Perez, Krzysztof Pietrzak, and Michael Walter. Grafting key-trees: Efficient key-management for overlapping groups. TCC 2021. [Full Version]
- Karen Klein. On the Adaptive Security of Graph-based Games. PhD Thesis at Institute of Science and Technology Austria (ISTA), 2021. [Full Version]
- Chethan Kamath, Karen Klein, Krzysztof Pietrzak, and Daniel Wichs. Limits on the adaptive security of Yao’s garbling. CRYPTO 2021. [Full Version]
- Benedikt Auerbach, Suvradip Chakraborty, Karen Klein, Guillermo Pascual-Perez, Krzysztof Pietrzak, Michael Walter, and Michelle Yeo. Inverse-sybil attacks in automated contact tracing. CT-RSA 2021. [Full Version]
- Karen Klein, Guillermo Pascual-Perez, Michael Walter, Chethan Kamath, Margarita Capretto, Miguel Cueto, Ilia Markov, Michelle Yeo, Joel Alwen, and Krzysztof Pietrzak. Keep the dirt: Tainted treekem, adaptively and actively secure continuous group key agreement. IEEE SP 2021. [Full Version]
- Hamza Abusalah, Chethan Kamath, Karen Klein, Krzysztof Pietrzak, and Michael Walter. Reversible proofs of sequential work. EUROCRYPT 2019. [Full Version]
- Georg Fuchsbauer, Chethan Kamath, Karen Klein, and Krzysztof Pietrzak. Adaptively secure proxy re-encryption. PKC 2019. [Full Version]
- Joël Alwen, Peter Gazi, Chethan Kamath, Karen Klein, Georg Osang, Krzysztof Pietrzak, Leonid Reyzin, Michal Rolinek, and Michal Rybár. On the memory-hardness of data-independent password-hashing functions. ACM ASIACCS 2018. [Full Version]
- Zahra Jafargholi, Chethan Kamath, Karen Klein, Ilan Komargodski, Krzysztof Pietrzak, and Daniel Wichs. Be adaptive, avoid overcommitting. CRYPTO 2017. [Full Version]
