Hayato KIMURA (木村 隼人)
- Security Researcher at Security Fundamentals Laboratory, NICT, Japan mainly applied cryptography and protocol security
- PhD Student at Cryptography Engineering Laboratory, The University of Osaka (Apr. 2025-Present, Supervisor: Prof. Takanori Isobe)
I'm a security researcher specializing in applied cryptography and protocol security. My research focuses on the security of real-world cryptographic protocols and privacy-enhancing technologies (PETs), including end-to-end encryption (E2EE). I have presented my work at major international security conferences such as IEEE EuroS&P, ACSAC, and Black Hat (USA & Asia).
Research interests: Applied Cryptography and Application Security
Security analysis and design of cryptographic protocols · Security analysis of symmetric key cryptography
Find me on
News
- Paper Jun. 2026: Our research paper has been accepted to USENIX WOOT 2026.
- Talk Jan. 2026: Our talk will be presented at Black Hat Asia 2026 Briefings.
- Paper Oct. 2025: Our research paper has been accepted to ACSAC 2025.
- Talk May 2025: Our talk will be presented at Black Hat USA 2025 Briefings (2025 acceptance rate: about 8%).
- Paper Feb. 2025: Our research paper has been accepted to IEEE EuroS&P 2025.
Work History
- Apr. 2025 – Present: NICT (National Institute of Information and Communications Technology), Japan
-
Apr. 2021 – Mar. 2025: LINE Corp (LY Corp), Japan
Note: LINE Corp merged with Yahoo Japan Corp to form LY Corporation in Oct. 2023
Education
- Apr. 2025 – Present: Ph.D. Program, Graduate School of Information Science and Technology
-
Apr. 2023 – Mar. 2025: Ph.D. Program, Graduate School of Information Science
Note: Transferred to The University of Osaka; degree not awarded.
- Apr. 2019 – Mar. 2021: Master's Degree in Information and Telecommunication Engineering
Publications
Peer-reviewed Journal Papers
- Shogo SHIRAKI, Hayato KIMURA, Takanori ISOBE, "Looking Further into the Security of End-to-End Encryption of SFrame, " Journal of Information Processing, vol.32, pp.679-689, Sep. 2024.
- Hayato KIMURA, Keita EMURA, Takanori ISOBE, Ryoma ITO, Kazuto OGAWA, and Toshihiro OHIGASHI, "A Deeper Look into Deep Learning-based Output Prediction Attacks Using Weak SPN Block Ciphers, " Journal of Information Processing, vol.31, pp.550-561, Sep. 2023.
- Toshihiro OHIGASHI, Shuya KAWAGUCHI, Kai KOBAYASHI, Hayato KIMURA, Tatsuya SUZUKI, Daichi OKABE, Takuya ISHIBASHI, Hiroshi YAMAMOTO, Maki INUI, Ryo MIYAMOTO, Kazuyoshi FURUKAWA, Tetsuya IZU, "Detecting Fake QR codes using Information from Error-Correction, " Journal of Information Processing, vol.29, pp.548-558, Sep. 2021.
- Keita EMURA, Hayato KIMURA, Toshihiro OHIGASHI, and Tatsuya SUZUKI, "Privacy-Preserving Aggregation of Time-Series Data with Public Verifiability from Simple Assumptions and Its Implementations, " The Computer Journal, pp.614-630, vol.62, Issue 4, Apr. 2019.
Peer-reviewed International Conference Papers
- Kota URUSHIGAKI, Hayato KIMURA, Atsushi TANAKA and Takanori ISOBE, "Practical Attacks on a Decentralized Secure Messenger Session, " 20th USENIX WOOT Conference on Offensive Technologies (WOOT 2026), Baltimore, MD, USA, (to appear), Aug. 10-11, 2026.
- Hayato KIMURA, Ryoma ITO, Kazuhiko MINEMATSU and Takanori ISOBE, "Gravity of the Situation: Security Analysis on Rocket.Chat E2EE, " 2025 Annual Computer Security Applications Conference (ACSAC 2025), Honolulu, Hawaii, USA, pp.15-30, Dec. 8-12, 2025.
- Hayato KIMURA, Ryoma ITO, Kazuhiko MINEMATSU, Shogo SHIRAKI and Takanori ISOBE, "Not in The Prophecies: Practical Attacks on Nostr, " 10th IEEE European Symposium on Security and Privacy (EuroS&P 2025), Venice, Italy, pp.585-606, Jun. 30 - Jul. 4, 2025.
- Hayato KIMURA, Keita EMURA, Takanori ISOBE, Ryoma ITO, Kazuto OGAWA, Toshihiro OHIGASHI, "Output Prediction Attacks on Block Ciphers using Deep Learning, " Proc. 4th International Workshop on Artificial Intelligence and Industrial Internet-of-Things Security (AIoTS 2022), Rome, Italy, ACNS 2022 Workshops, LNCS 13285,, Rome, Italy, pp.248–276, Jun. 22-23, 2022.
- Hayato KIMURA, Takanori ISOBE, and Toshihiro OHIGASHI, "Neural-Network-Based Pseudo-Random Number Generator Evaluation Tool for Stream Ciphers, " Proc. CANDAR Workshops 2019, WCIS 2019, Nagasaki, Japan, pp.333-338, Nov. 26-29, 2019.
- Tohru KONDO, Hidenobu WATANABE, Kai KOBAYASHI, Hayato KIMURA, and Toshihiro OHIGASHI, "Development of the Edge Computing Platform with Dynamic Modular Configuration for an IoT Platform, " Proc. PACRIM 2019, Victoria, B.C., Canada, 6 pages, Aug. 21-23, 2019.
- Tatsuya SUZUKI, Keita EMURA, Hayato KIMURA, and Toshihiro OHIGASHI, "Implementation Results of Privacy-Preserving and Public Verifiable Data Aggregation Protocols, " The 12th International Workshop on Security (IWSEC 2017), poster, Aug. 2017
ePrint
- Hayato Kimura, Keita Emura, Takanori Isobe, Ryoma Ito, Kazuto Ogawa, Toshihiro Ohigashi, "Output Prediction Attacks on Block Ciphers using Deep Learning, " Cryptology ePrint Archive, 2021/401, 33 pages, IACR, 2021, https://eprint.iacr.org/2021/401.pdf
Talks (non-archival)
- Hayato KIMURA, Ryoma ITO, Kazuhiko MINEMATSU and Takanori ISOBE, "Payload Compromised: Full Key Recovery in Rocket.Chat E2EE, " Black Hat Asia 2026 Briefings, Apr. 23-24, 2026.
- 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, Aug. 6, 2025.
Awards
-
JIP Specially Selected Paper (Sep. 2023) (URL)
- Hayato KIMURA, Keita EMURA, Takanori ISOBE, Ryoma ITO, Kazuto OGAWA, and Toshihiro OHIGASHI, "A Deeper Look into Deep Learning-based Output Prediction Attacks Using Weak SPN Block Ciphers, "
-
IWSEC 2017 Best Poster Award (Aug. 2017) (URL)
- Tatsuya SUZUKI, Keita EMURA, Hayato KIMURA, and Toshihiro OHIGASHI, "Implementation Results of Privacy-Preserving and Public Verifiable Data Aggregation Protocols, " The 12th International Workshop on Security (IWSEC 2017)