I’m kei5uke, a full-stack software engineer who also does security testing from time to time.
I’m passionate about cybersecurity and enjoy playing CTFs.
This blog is my personal record of the CTF machines I’ve hacked and how I did it.
See all writeups in CTF.
CV
Contact Information
Email: keisuke.konno.tech AT gmail.com
GitHub: kei5uke
Skills
- Programming Languages
- Frequently used: JavaScript, TypeScript, Python, C
- Previous experience: Java, PHP, C++, R, Go
- Full-stack development (frontend and backend)
- Infrastructure as Code: Ansible
- Basic network engineering: TCP/IP, LAN/WAN
- Algorithms and data structures
- Implementation of machine learning and deep learning algorithms
Experience
Software Engineer / Penetration Tester
NTNU | HUNT Cloud, Norway · September 2025 - Present
- Working on secure cloud platforms for sensitive data in medical and health research.
Software Engineer (AI/ML)
Flowstep OÜ, Estonia · 2024
- Developed a web application that helps designers create better UI/UX using LLMs and computer vision.
- Built the full stack with React and Node.js.
- Fine-tuned a vision transformer model (SAM) for computer vision features using PyTorch and OpenCV.
Software Engineer (Full-stack)
Hemlex OÜ, Estonia · August 2022 - December 2023
- Developed an educational web application for teachers and students.
- Designed pages and components with React and TypeScript.
- Implemented a RESTful API with Node.js and Express.js, including JWT-based authentication.
- Tested the frontend and backend with Cypress and Jest.
- Conducted OWASP-based security testing for XSS, SQL injection, authentication flaws, CSRF, broken access control, and more.
Research Intern, e-Healthcare Technology Lab
Turku University of Applied Sciences, Finland · August 2019 - February 2020
- Built an e-healthcare application that lets patients with disabilities control home appliances with their brain waves.
- Implemented it in Python using a deep learning model (Long Short-Term Memory network).
- Conducted time-series analysis of patients’ biometric data, such as brain waves, body temperature, and skin resistance.
- Wrote Bash scripts to collect sensor data from IoT devices.
Education
Master of Science in Cybersecurity
Tallinn University of Technology, Estonia · 2023 - 2025
Exchange Study
Norwegian University of Science and Technology, Norway · 2025
Bachelor of Science in Cyber Security Engineering
Tallinn University of Technology, Estonia · 2020 - 2023
Thesis: Multi-class Classification of Botnet Detection by Active Learning
Foundation Degree in Network Engineering
National Institute of Technology, Sendai College, Japan · 2015 - 2020
Thesis: Biometric Engineering Research: Biometric Measurement and Its Application