Denis Kasak
Head Of Security at Freelance
Croatia
Summary
🤩
Rockstar🎓
Top SchoolDenis Kasak is a seasoned security researcher and engineer with 16 years of experience, currently leading security programs at Element and The Matrix.org Foundation while running his own consultancy, Narsil. He combines deep systems expertise in Linux and FreeBSD with strong programming skills across Python, Rust, Haskell, C and C++, and a firm grounding in algorithms and formal methods. Denis specializes in application and protocol security—particularly Matrix, web, Android and native binaries—and has improved core projects like Synapse and matrix-rust-sdk to harden encryption and input handling. An active open-source contributor, he balances pragmatic bug fixes and compatibility work (e.g., Gambit and urlwatch) with localization and usability improvements, and he regularly translates research papers into actionable defenses. Based in Croatia, he brings a rare mix of formal thinking (type theory and category interests) and hands-on exploitation, fuzzing and secure-coding practice.
15 years of coding experience
3 years of employment as a software developer
Master of Computer Engineering Computer Engineering, Master of Computer Engineering Computer Engineering at FERIT Osijek
Stackoverflow
2,671reputation
331kreached
59answers
0questions
Github Skills (59)
algorithm10
crypto10
markdown10
debug10
debugging10
javascript10
c-language10
matrix10
python10
back-end-development10
translation10
testing10
it-security10
internationalization10
colors10
Programming languages (26)
Github contributions (5)
poljar/weechat-matrix
Feb 2018 - Apr 2022
Weechat Matrix protocol script written in python
Role in this project:
Back-end Developer
Back-end DeveloperContributions:65 commits, 31 PRs, 15 pushes in 4 years 2 months
Contributions summary:Denis primarily contributed to the Weechat Matrix protocol script, focusing on improving its functionality and usability. Their work included refactoring color handling, implementing the `/kick` command, and integrating Weechat proxy support. Additionally, the user made several improvements to error and help messages, enhancing the user experience. Furthermore, they introduced a variety of bug fixes.
pythonmatrixweechatmatrix-protocol
matrix-org/matrix-rust-sdk
Mar 2020 - Jan 2023
Matrix Client-Server SDK for Rust
Role in this project:Back-end Developer
Back-end DeveloperContributions:105 reviews, 113 commits, 20 PRs in 2 years 10 months
Contributions summary:Denis primarily contributed to the Matrix Rust SDK, focusing on improving its core functionalities and maintainability. Their work includes adding and refactoring methods for room display name calculations and disambiguation, which is crucial for client-side user experience. They also addressed bugs in the sync token mechanism to ensure that the responses are correctly interpreted by Matrix clients. The user's changes involve core models and base libraries within the SDK.
rustclient-serversdkmatrixmatrix-client
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