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Biography#

I am a security researcher focused on threat analysis, practical defensive design, and security protocols. I also contribute to software engineering and data analysis to empirically validate ideas. Outside of research, I enjoy working on security challenges.

Publications (Selected)#

  • "Integration of PSI-CA and Differential Privacy for APPI Compliance"
    （個人情報保護法準拠に資するPSI-CAと差分プライバシーの統合設計）
    Authors: Kabuto Okajima Diaz Zazueta, Koji Chida
    Venue: The 111th IPSJ SIG Computer Security (CSEC) Joint Research Meeting, Niigata, Japan
    Date: December 2, 2025
    Short abstract: It proposes a workflow aligned with Japan’s APPI that integrates PSI-CA with differential privacy for cross-organizational analytics, mapping legal requirements to concrete technical parameters and deployment assumptions.

  • "Block Hijacking Attack: Impact Evaluation on Liquid Network and Design Insights for Blockchain-based Scaling Solutions"
    Authors: Kabuto Okajima, Shin’ichiro Matsuo, Koji Chida
    Proceedings: 2025 IEEE International Conference on Blockchain and Cryptocurrency (ICBC), Pisa, Italy
    Date: June 2, 2025
    Short abstract: It presents and evaluates the Block Hijacking Attack—an economically rational DoS that disrupts other users’ transactions—demonstrated on the Liquid Network, in collaboration with engineers at Blockstream.

  • "A Study on Anonymization Through Participation in iPWS Cup 2023"
    Authors: Kabuto Okajima, Koji Chida
    Proceedings: International Workshop on Security, IWSEC 2024, Kyoto, Japan
    Date: September 17, 2024
    Short abstract: It reviews and extends the anonymization methods and re-identification attacks we developed for iPWS Cup 2023—an international anonymization competition—building on our first-place solution.

Experience#

  • Research Assistant / M.S. Student, Georgetown University — Washington, DC, USA · Jan 2026–present
  • Head of Engineering, Physical Control Center — Osaka, Japan · Mar 2024–present
  • Researcher, Gunma University — Gunma, Japan · Apr 2025–Dec 2025
  • Researcher, Commonwealth Cyber Initiative — Virginia, USA · Mar 2024–Dec 2024
  • Software Engineer, multiple companies · Feb 2022–Jul 2025 (combined experience)

Highlights#