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RYOMA ITO

RYOMA ITO

Research Manager
Security Fundamentals Laboratory
Cybersecurity Research Institute

Ryoma Ito received the B.E. degree from the National Defense Academy of Japan in 2009, the M.S. degree from the Japan Advanced Institute of Science and Technology in 2015, and the Ph.D. degree in engineering from Osaka University in 2019. From 2009 to 2020, he served in Japan Air Self-Defense Force, Ministry of Defense, Japan. He joined the National Institute of Information and Communications Technology (NICT), Japan, as a Senior Researcher in 2020, and is currently a Planning Manager at the Strategic Planning Office and a Research Manager at the Security Fundamentals Laboratory. His research interests include the cryptanalysis and design of symmetric key ciphers and security analysis of real-world systems, particularly end-to-end encryption technologies used in messaging applications and video conferencing systems. He received the SCIS Paper Award in 2015, the CSS Encouragement Award in 2021, the SCIS Innovation Paper Award in 2021, the IPSJ Yamashita SIG Research Award in 2022, the SCIS Innovation Paper Award in 2024, the CSS Best Paper Award in 2025, and more.

Research interests
Cryptanalysis and Design of Symmetric Key Ciphers, Security Analysis of Real-world Systems
Keyword
Symmetric Key Cryptography, Lightweight Cryptography, End-to-End Encryption

Selected papers

  • Subhadeep Banik, Tatsuya Ishikawa, Takanori Isobe, Ryoma Ito, Kazuhiko Minematsu, Kazuma Nakata, Mostafizar Rahman, and Kosei Sakamoto. Dialga: A Family of Low-Latency Tweakable Block Ciphers using Multiple Linear Layers. IACR Transactions on Symmetric Cryptology, Vol. 2025, Issue 4, pp. 70-124, Dec. 2025.
  • Takoro Shiraya, Subhadeep Banik, Tatsuya Ishikawa, Ryoma Ito, Mostafizar Rahman, Kosei Sakamoto, Atsushi Tanaka, Shion Utsumi, and Takanori Isobe. Exploring SHA Instructions and Its Application to AES-based Schemes. IACR Communications in Cryptology, Vol. 2, Issue 3, Oct. 2025.
  • Kosei Sakamoto, Ryoma Ito, and Takanori Isobe. Parallel SAT Framework to Find Clustering of Differential Characteristics and Its Applications. Journal of Information Security and Applications, vol. 94, no. 104203, Sep. 2025. (IF = 3.7).
  • Hayato Kimura, Ryoma Ito, Kazuhiko Minematsu, Shogo Shiraki, and Takanori Isobe. Not Sealed: Practical Attacks on Nostr, a Decentralized Censorship-Resistant Protocol. Black Hat USA 2025 Briefings, 2025.8.6. (Speaker: Hayato Kimura) (Acceptance Rate: 8.2% = 93/1143)
  • Kazuma Taka, Kosei Sakamoto, Ryoma Ito, Rentaro Shiba, Shion Utsumi, and Takanori Isobe. Divide-and-Conquer SAT for Exploring Optimal Differential and Linear Characteristics and Its Applications. IACR Transactions on Symmetric Cryptology, Vol. 2025, Issue 3, pp. 516-576, Sep. 2025.
  • Hayato Kimura, Ryoma Ito, Kazuhiko Minematsu, and Takanori Isobe. Gravity of the Situation: Security Analysis on Rocket.Chat E2EE. In 41th IEEE Annual Computer Security Applications Conference - ACSAC 2025, pages 15-30. IEEE, 2025. (acceptance rate: 20.7% = 84/406)
  • Hayato Kimura, Ryoma Ito, Kazuhiko Minematsu, Shogo Shiraki, and Takanori Isobe. Not in The Prophecies: Practical Attacks on Nostr. In 10th IEEE European Symposium on Security and Privacy - EuroS&P 2025, pages 585-606. IEEE, 2025. (acceptance rate: 21.9% = 60/273)
  • Hayato Watanabe, Ryoma Ito, and Toshihiro Ohigashi. On the Effects of Neural Network-based Output Prediction Attacks on the Design of Symmetric-key Ciphers. Journal of Information Security and Applications, vol. 90, no. 104046, May. 2025. (IF = 3.8).
  • Takanori Isobe, Ryoma Ito, and Kazuhiko Minematsu. Security Analysis of SFrame. Journal of Information Security and Applications, vol. 89, no. 103958, Mar. 2025. (IF = 3.8).
  • Kodai Taiyama, Kosei Sakamoto, Ryoma Ito, Kazuma Taka, and Takanori Isobe. Key Collisions on AES and Its Applications. In Kai-Min Chung and Yu Sasaki, editors, Advanced in Cryptology - Asiacrypt 2024, volume 15490 of Lecture Notes in Computer Science, pages 267–300. Springer International Publishing, 2024. (acceptance rate: 29.2% = 127/435)

Awards

  • Oct. 2025, CSS Best Paper Award, Computer Security Symposium 2025 (CSS 2025), IPSJ.
  • Jan. 2025, SCIS Innovation Paper Award, The 42nd Symposium on Cryptography and Information Security (SCIS 2024), Institute of Electronics, Information and Communication Engineers (IEICE).
  • Oct. 2024, CSS Paper Award, Computer Security Symposium 2024 (CSS 2024), IPSJ.
  • Oct. 2024, CSS Ethical Practice Award, Computer Security Symposium 2024 (CSS 2024), IPSJ.
  • Jun. 2024, NICT Outstanding Achievement Award, National Institute of Information and Communications Technology (NICT).
  • Mar. 2023, IPSJ Yamashita SIG Research Award, Information Processing Society of Japan (IPSJ).
  • Jan. 2022, SCIS Innovation Paper Award, The 39th Symposium on Cryptography and Information Security (SCIS 2021), Institute of Electronics, Information and Communication Engineers (IEICE).
  • Oct. 2021, CSS Encouragement Research Award, Computer Security Symposium 2021 (CSS 2021), IPSJ.
  • Jun. 2021, NICT Outstanding Achievement Award, National Institute of Information and Communications Technology (NICT).
  • Jan. 2016, SCIS Paper Award, The 34th Symposium on Cryptography and Information Security (SCIS 2015), IEICE.
  • Mar. 2015, Best Student Award, Japan Advanced Institute of Science and Technology.
  • Mar. 2009, Best Student Award, National Defense Academy.
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