I am Mathias Hall-Andersen (“rot256” on the internet), a PhD in theoretical cryptology (from Aarhus University) with a broad interest in both theoretical and practical information security, as well as privacy enhancing technologies including: cryptography, cryptanalysis, coding theory, reverse engineering, vulnerability research and anything which lies in the intersection. I love building and breaking real-world systems; particularly when they involve cryptography, with a soft spot for succinct arguments (SNARKs).

Now I am working with ZKSecurity which does security auditing and engineering for advanced cryptography with a focus on zero-knowledge type applications: SNARKs, recursive proofs, anonymous credentials etc. If you are building with such technologies, or planning to build with them, you should reach out to us: because of our strong team and focus, we find bugs that many others miss.

In my free time I play/organize CTFs with Kalmarunionen / Norsecode, I also work on open source software and enjoy various types of swing dancing. On this site I post cryptography related technical content, ideas too small for a paper, projects I have been working on and write-ups for CTF challenges (usually exploitation / reversing / cryptography challenges).


2024 (spring)PhD Thesis (Either/Or)Aarhus University (CS Dept.)
2020 - 2024PhD in Theoretical CryptographyAarhus University (CS Dept.)
2022 (fall)Visiting ResearcherBoston University (BUSec)
2017 - 2020Master in Computer ScienceUniversity of Copenhagen
2019 (fall)Master Thesis (Contingent Payments)Aarhus University
2018 (fall)ExchangeETH Zürich (D-INFK)
2017Bachelor Thesis (Linear Cryptanalysis)Technical University of Denmark
2014 - 2017Bachelor in Computer ScienceUniversity of Copenhagen


2024 -Senior Consultant/Cryptographer.ZKSecurity
2020 - 2024PhD StudentAarhus University
2023 (summer)Internship, Research / Engineering, FromagerGalois
2022 (summer)Internship, Cryptographic Engineering (Rust)O(1) Labs
2021 (summer)Internship (Development/Research on DARPA SIEVE)Trail of Bits
2020 (fall)Instructor in Distributed Systems and SecurityAarhus University
2020 (summer)Internship (Development/Research on DARPA SIEVE)Trail of Bits
2020 (spring)External lecturer in Proactive Computer SecurityUniversity of Copenhagen
2019 (fall)Open source development on WireGuard-rs
(NGI; Next-Generation Internet grant)
NLnet (Sponsor)
2019 (spring)Instructor in Proactive Computer SecurityUniversity of Copenhagen
2018 (summer)Internship (Security Consultant – Cryptography)NCC Group, New York
(Cryptography Services)
2017 (fall) - 2018Teaching Assistant in Practical CryptologyTechnical University of Denmark
2017 (summer)Google Summer of Code (created WireGuard-go)WireGuard (Linux Foundation)
2016 (fall)Instructor in Computer SystemsUniversity of Copenhagen
2016Student AssistantDeloitte Cyber Risk Services
2015Java ProgrammerSkandinaviska Enskilda Banken





Fluent in Danish, English, Rust, Python, Sage, C, Go, LaTex, a slew of assembly languages and cryptographic jargon.

Shaky in a lot more…


A few examples of my technical writing:


Personal Email\(\text{math}\)\(\text{ias}\)\(@\)\(\text{hall-an}\text{dersen.dk}\)
PGP Key/key.asc or keybase.io, Fingerprint: 71e1ec2b778745710667d51dae331b20b3c8a5c2
Websiterot256.dev – you are looking at it.

Questions? Comments? Interesting projects? Need help building/breaking cryptography?

Feel free to drop me an email :)