Doctral Thesis

1. • Takuya Hayashi,
   • "Experiments on Discrete Logarithm Problems in GF(3^6n)",
   • Kyushu University, 2013.

Journal Papers

1. • Yuji Koike, Takuya Hayashi, Jun Kurihara, and Takanori Isobe,
   • "Virtual Vault: A Practical Leakage Resilient Scheme Using Space-Hard Ciphers",
   • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.104-A, No.1, pp.182-189, 2021.
2. • Hiromi Arai, Keita Emura, and Takuya Hayashi,
   • "Privacy-Preserving Data Analysis: Providing Traceability without Big Brother",
   • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.104-A, No.1, pp.2-19, 2021.
3. • Keita Emura, Takuya Hayashi, and Ai Ishida,
   • "Group Signatures with Time-bound Keys Revisited: A New Model, an Efficient Construction, and its Implementation",
   • IEEE Transactions on Dependable and Secure Computing, Vol.17, No.2, pp.292-305, 2020.
4. • Keita Emura and Takuya Hayashi,
   • "A Revocable Group Signature Scheme with Scalability from Simple Assumptions",
   • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.103-A, No.1, pp.125-140, 2020.
5. • Keita Emura and Takuya Hayashi,
   • "Road-to-Vehicle Communications with Time-Dependent Anonymity: A Light Weight Construction and its Experimental Results",
   • IEEE Transactions on Vehicular Technology, Vol.67, No.2, pp.1582-1597, 2018.
6. • Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, Lihua Wang, and Shiho Moriai,
   • "Privacy-Preserving Deep Learning via Additively Homomorphic Encryption",
   • IEEE Transactions on Information Forensics & Security, Vol.13, No.5, pp.1333-1345, 2018.
7. • Yoshinori Aono, Takuya Hayashi, Le Trieu Phong, and Lihua Wang,
   • "Efficient Homomorphic Encryption with Key Rotation and Security Update",
   • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.101-A, No.1, 2018.
8. • Yoshinori Aono, Takuya Hayashi, Le Trieu Phong, and Lihua Wang,
   • "Input and Output Privacy-Preserving Linear Regression",
   • IEICE Transactions on Information and Systems, Vol.100-D, No.10, pp.2339-2347, 2017.
9. • Yoshinori Aono, Takuya Hayashi, Le Trieu Phong, and Lihua Wang,
   • "Privacy-Preserving Logistic Regression with Distributed Data Sources via Homomorphic Encryption",
   • IEICE Transactions on Information and Systems, Vol.99-D, No.8, pp.2079-2089, 2016.
10. • Naoyuki Shinohara, Takeshi Shimoyama, Takuya Hayashi, and Tsuyoshi Takagi,
    • "Key Length Estimation of Pairing-Based Cryptosystems using EtaT Pairing",
    • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.97-A, No.1, pp.236-244, 2014.
11. • Takuya Hayashi, Naoyuki Shinohara, Lihua Wang, Shin'ichiro Matsuo, Masaaki Shirase, and Tsuyoshi Takagi,
    • "Solving a 676-bit Discrete Logarithm Problem in GF(3^6n)",
    • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.95-A, No.1, pp.204-212, 2012.

International Conference Papers

1. • Akira Nakashima, Takuya Hayashi, Hikaru Tsuchida, Yukimasa Sugizaki, Kengo Mori, and Toshiyuki Isshiki,
   • "Faster Homomorphic Evaluation of Arbitrary Bivariate Integer Functions via Homomorphic Linear Transformation",
   • 12th Workshop on Encrypted Computing & Applied Homomorphic Cryptography (WAHC 2024) pp.76-86, 2024.
2. • Yukimasa Sugizaki, Hikaru Tsuchida, Takuya Hayashi, Koji Nuida, Akira Nakashima, Toshiyuki Isshiki, and Kengo Mori,
   • "Threshold Fully Homomorphic Encryption over the Torus",
   • 28th European Symposium on Research in Computer Security (ESORICS 2023), Lecture Notes in Computer Science, Vol.14344, pp.45-65, 2023.
3. • Yuji Koike, Kosei Sakamoto, Takuya Hayashi, and Takanori Isobe,
   • "Galaxy: A Family of Stream-Cipher-Based Space-Hard Ciphers",
   • 25th Australasian Conference on Information Security and Privacy (ACISP 2020), Lecture Notes in Computer Science, Vol.12248, pp.142-159, 2020.
4. • Takehiro Tezuka, Lihua Wang, Takuya Hayashi, and Seiichi Ozawa,
   • "A Fast Privacy-Preserving Multi-Layer Perceptron Using Ring-LWE Based Homomorphic Encryption",
   • 2nd International Workshop on Cross-disciplinary Data Exchange and Collaboration (CDEC), Workshop on IEEE International Conference on Data Mining (ICDM 2019), 2019.
5. • Sangwook Kim, Masahiro Omori, Takuya Hayashi, Toshiaki Omori, Lihua Wang, and Seiichi Ozawa,
   • "Privacy-Preserving Naive Bayes Classification Using Fully Homomorphic Encryption",
   • 25th International Conference on Neural Information Processing (ICONIP 2018), Lecture Notes in Computer Science, Vol.11304, pp.349-358, 2018.
6. • Keita Emura and Takuya Hayashi,
   • "A Revocable Group Signature Scheme with Scalability from Simple Assumptions and Its Implementation”,
   • 21st Information Security Conference (ISC 2018), Lecture Notes in Computer Science, Vol.11060, pp.442-460, 2018.
7. • Shohei Kuri, Takuya Hayashi, Toshiaki Omori, Seiichi Ozawa, Yoshinori Aono, Le Trieu Phong, Lihua Wang, and Shiho Moriai,
   • "Privacy Preserving Extreme Learning Machine using Additively Homomorphic Encryption",
   • 2017 IEEE Symposium Series on Computational Intelligence (SSCI 2017), 2017.
8. • Hiromi Arai, Keita Emura, and Takuya Hayashi,
   • "A Framework of Privacy Preserving Anomaly Detection: Providing Traceability without Big Brother",
   • 16th Workshop on Privacy in the Electronic Society (WPES 2017), pp.111-122, 2017.
9. • Lihua Wang, Takuya Hayashi, Yoshinori Aono, and Le Trieu Phong,
   • "A Generic yet Efficient Method for Secure Inner Product",
   • 11th International Conference on Network and System Security (NSS 2017), Lecture Notes in Computer Science, Vol.10394, pp.217-232, 2017.
10. • Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, Lihua Wang, and Shiho Moriai,
    • "Privacy-Preserving Deep Learning: Revisited and Enhanced",
    • 8th International Conference on Applications and Technologies in Information Security (ATIS 2017), Communications in Computer and Information Science, Vol.719, pp.100-110, 2017.
11. • Yoshinori Aono, Takuya Hayashi, Le Trieu Phong, and Lihua Wang,
    • "Efficient Key-Rotatable and Security-Updatable Homomorphic Encryption",
    • 5th International Workshop on Security in Cloud Computing (SCC 2017), pp.35-42, 2017.
12. • Keita Emura, Takuya Hayashi, Noboru Kunihiro, and Jun Sakuma,
    • "Mis-operation Resistant Searchable Homomorphic Encryption",
    • 12th ACM Asia Conference on Computer and Communications Security (ASIACCS 2017), pp.215-229, 2017.
13. • Keita Emura, Takuya Hayashi, and Ai Ishida,
    • "Group Signatures with Time-bound Keys Revisited: A New Model and an Efficient Construction",
    • 12th ACM Asia Conference on Computer and Communications Security (ASIACCS 2017), pp.777-788, 2017.
14. • Keita Emura, Takuya Hayashi, and Shiho Moriai,
    • "Toward Securing Tire Pressure Monitoring Systems: A Case of PRESENT-based implementation",
    • International Symposium on Information Theory and Its Applications (ISITA 2016), pp.403-407, 2016.
15. • Yoshinori Aono, Yuntao Wang, Takuya Hayashi, and Tsuyoshi Takagi,
    • "Improved Progressive BKZ Algorithms and Their Precise Cost Estimation by Sharp Simulator",
    • 35th Annual International Conference on the Theory and Applications of Cryptographic Techniques (EUROCRYPT 2016), Lecture Notes in Computer Science, Vol.9665, pp.789-819, 2016.
16. • Keita Emura and Takuya Hayashi,
    • "A Light-weight Group Signature Scheme with Time-token Dependent Linking",
    • 4th International Workshop on Lightweight Cryptography for Security & Privacy (LightSec 2015), Lecture Notes in Computer Science, Vol.9542, pp.37-57, 2016.
17. • Takuya Hayashi, Takeshi Shimoyama, Naoyuki Shinohara, and Tsuyoshi Takagi,
    • "Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)",
    • 18th Annual International Conference on the Theory and Application of Cryptology and Information Security (ASIACRYPT 2012), Lecture Notes in Computer Science, Vol.7658, pp.46-60, 2012.
18. • Naoyuki Shinohara, Takeshi Shimoyama, Takuya Hayashi, and Tsuyoshi Takagi,
    • "Key Length Estimation of Pairing-Based Cryptosystems using EtaT Pairing",
    • 8th International Conference on Information Security Practice and Experience (ISPEC 2012), Lecture Notes in Computer Science, Vol.7232, pp.228-244, 2012.
19. • Takuya Hayashi, Naoyuki Shinohara, Lihua Wang, Shin'ichiro Matsuo, Masaaki Shirase, and Tsuyoshi Takagi,
    • "Solving a 676-bit Discrete Logarithm Problem in GF(3^6n)",
    • 13th International Conference on Practice and Theory in Public Key (PKC 2010), Lecture Notes in Computer Science, Vol.6056, pp.351-367, 2010.

Posters

1. • Yuji Koike, Takuya Hayashi, and Takanori Isobe,
   • "A Practical Leakage-Resilient Scheme using Big-key Encryptions",
   • 14th International Workshop on Security (IWSEC 2019) Poster Session, 2019.
2. • Sangwook Kim, Toshiaki Omori, Masahiro Omori, Takuya Hayashi, Lihua Wang, and Seiichi Ozawa,
   • "Privacy-Preserving Naive Bayes Classifier based on Homomorphic Encryption",
   • 13th International Workshop on Security (IWSEC 2018) Poster Session, 2018.
3. • Takuya Hayashi, Shohei Kuri, Toshiaki Omori, Seiichi Ozawa, Yoshinori Aono, Le Trieu Phong, Lihua Wang, and Shiho Moriai,
   • "Privacy-Preserving Machine Learning via Additively Homomorphic Encryption: the Case of Linear and Logistic Regressions",
   • Private and Secure Machine Learning 2017 (PSML 2017), Workshop on 34th International Conference on Machine Learning (ICML 2017), 2017. (Peer-reviewd)
4. • Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, Lihua Wang, and Shiho Moriai,
   • "Privacy-Preserving Deep Learning: Revisited and Enhanced",
   • Private and Secure Machine Learning 2017 (PSML 2017), Workshop on 34th International Conference on Machine Learning (ICML 2017), 2017. (Peer-reviewd)
5. • Yoshinori Aono, Takuya Hayashi, Le Trieu Phong, and Lihua Wang,
   • "CODASPY'16 Poster / Scalable and Secure Logistic Regression via Homomorphic Encryption",
   • 6th ACM Conference on Data and Application Security and Privacy (ACM CODASPY 2016), pp.142-144, 2016. (Peer-reviewd)
6. • Lihua Wang, Takuya Hayashi, Sachiko Kanamori, Atsushi Waseda Ryo Nojima, and Shiho Moriai,
   • "POSTER: PRINCESS: A Secure Cloud File Storage System for Managing Data with Hierarchical Levels of Sensitivity",
   • ACM Conference on Computer and Communications Security 2015 (ACM CCS 2015), pp.1684-1686, 2015. (Peer-reviewd)

Talks

1. • Takuya Hayashi,
   • "Privacy-preserving Data Mining via Homomorphic Encryption",
   • IMI Cryptography Seminar, 2017.
2. • Takuya Hayashi,
   • "Cryptanalysis of Pairing-based Cryptosystems over Small Characteristic Fields",
   • Young Researcher Session in Forum Mathematics for Industry 2013 (FMI 2013), 2013.
   • Proceeding: The Impact of Applications on Mathematics, Mathematics for Industry, Vol.1, pp.167-176, 2014.
3. • Takuya Hayashi,
   • "Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)",
   • IMI Cryptography Seminar, 2012.
4. • Takuya Hayashi,
   • "Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)",
   • 16th Workshop on Elliptic Curve Cryptography (ECC 2012), 2012.
5. • Takuya Hayashi, Takeshi Shimoyama, Naoyuki Shinohara and Tsuyoshi Takagi,
   • "Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)",
   • Rump Session in CRYPTO 2012, 2012.

Bulletins

1. • Keita Emura, Miyako Ohkubo, Takuya Hayashi,
   • "Research on Security Improvement for Homomorphic Encryption Towards privacy-preserving data mining for personal data",
   • NICT NEWS, Vol.2019.2, No.474, pp.4-5, 2019.
2. • Naoyuki Shinohara, Yoshinori Aono, Shoko Kanamori, Takashi Kurokawa, Takuya Hayashi, Le Trieu Phong,
     
   • "Research and Standardization of Post-Quantum Cryptography Measures against quantum computer threats on cryptosystems",
   • NICT NEWS, Vol.2019.2, No.474, pp.6-7, 2019.
3. • Le Trieu Phong, Takuya Hayashi, Yoshinori Aono, Takuma Ito,
   • "Privacy-Preserving Data Analytics",
   • NICT NEWS, Vol.2019.2, No.474, pp.8-9, 2019.
4. • Takuya Hayashi,
   • "Cryptographic Implementations −Achieving both efficiency and security−",
   • NICT NEWS, Vol.2019.2, No.474, pp.13, 2019.
5. • Naoyuki Shinohara, Yoshinori Aono, and Takuya Hayashi,
   • "Recent Developments in Security Evaluation Technologies of Cryptosystems",
   • Journal of the National Institute of Information and Communications Technology, Special Issue on Network Security, Vol.63, No.2, pp.189-195, 2016.
6. • Lihua Wang, Takuya Hayashi, Atsushi Waseda, Ryo Nojima, and Shiho Moriai,
   • "An Encrypted File Storage System with Hierarchical Levels of Sensitivity and its Applications",
   • Journal of the National Institute of Information and Communications Technology, Special Issue on Network Security, Vol.63, No.2, pp.215-221, 2016.
7. • Ryo Nojima, Sachiko Kanamori, Atsushi Waseda, Keita Emura, and Takuya Hayashi,
   • "Privacy Preserving Technologies for Personal Data",
   • Journal of the National Institute of Information and Communications Technology, Special Issue on Network Security, Vol.63, No.2, pp.229-233, 2016.
8. • Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, and Lihua Wang,
   • "Long Term Cryptography and Applications to Privacy-Preserving Data Mining",
   • Journal of the National Institute of Information and Communications Technology, Special Issue on Network Security, Vol.63, No.2, pp.235-240, 2016.
9. • Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, and Lihua Wang,
   • SPHERE: A New Encryption Scheme Allowing Both Security Updates and Operations on Encrypted Data
   • NICT NEWS, Vol.2015.3, No.450, pp.3-4, 2015.

Editors

1. • Shun'ichi Yokoyama, Norie Fu, and Takuya Hayashi (ed.),
   • "Progress in Computer Algebra Systems",
   • Mathematics-for-Industry Lecture Note Series Vol.35, 210 pages, 2011.

Other Works

1. • Le Trieu Phong, Takuya Hayashi, Yoshinori Aono, and Shiho Moriai,
   • "LOTUS - Learning with errOrs based encryption with chosen ciphertexT secUrity for poSt quantum era",
   • A submission for NIST Post-Quantum Cryptography Standardization, 2017.
     

Organizing Activities

Organizing Committee

• International Workshop on Security (IWSEC), 2016, 2017, 2018.
• ACM Symposium on Information, Computer and Communications Security (ASIACCS), 2014.

Program Committee

• IEEE Cyber Science and Technology Congress (CyberSciTech), 2019.
• International Symposium on Computing and Networking (CANDAR), 2016, 2017.
• International Workshop on Information and Communication Security (WICS), 2016, 2017.

Awards

1. • IEEE Signal Processing Society, 2023 Best Paper Awards,
   • "Privacy-Preserving Deep Learning via Additively Homomorphic Encryption".
2. • 14th International Workshop on Security (IWSEC 2019), Best Poster Awards,
   • "A Practical Leakage-Resilient Scheme using Big-key Encryptions".

Full list containing local journals/conferences/talks/awards is shown in Japanese version.