Publications

For a complete list of publications including domestic conferences, please see the Japanese page.

Doctoral Thesis

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

Journal Papers

Peer-Reviewed
Akira Nakashima, Yukimasa Sugizaki, Hikaru Tsuchida, Takuya Hayashi, Koji Nuida, Kengo Mori, and Toshiyuki Isshiki
Multi-Key Homomorphic Encryption with Threshold Re-Encryption via (Replicated) Additive Secret Sharing
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol.109-A, No.3, pp.246-258, 2026.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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, pp.39-50, 2018.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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

Peer-Reviewed
Akira Nakashima, Yukimasa Sugizaki, Hikaru Tsuchida, Takuya Hayashi, Koji Nuida, Kengo Mori, and Toshiyuki Isshiki
Multi-key Homomorphic Encryption with Threshold Re-encryption
31st International Conference on Selected Areas in Cryptography (SAC 2024), Lecture Notes in Computer Science, Vol.15516, pp.84-104, 2024.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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.
Peer-Reviewed
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

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.
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.
Peer-Reviewed
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-Reviewed
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-Reviewed
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-Reviewed
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.

Talks

Invited Talks
Takuya Hayashi
Privacy-preserving Data Mining via Homomorphic Encryption
IMI Cryptography Seminar, 2017.
Takuya Hayashi
Cryptanalysis of Pairing-based Cryptosystems over Small Characteristic Fields
Young Researcher Session in Forum Mathematics for Industry 2013 (FMI 2013), 2013.
Invited Talks
Takuya Hayashi
Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)
IMI Cryptography Seminar, 2012.
Invited Talks
Takuya Hayashi
Breaking Pairing-Based Cryptosystems using EtaT Pairing over GF(3^97)
16th Workshop on Elliptic Curve Cryptography (ECC 2012), 2012.
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.

Proceedings

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.

Bulletins

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.
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.
Le Trieu Phong, Takuya Hayashi, Yoshinori Aono, Takuma Ito
Privacy-Preserving Data Analytics
NICT NEWS, Vol.2019.2, No.474, pp.8-9, 2019.
Takuya Hayashi
Cryptographic Implementations −Achieving both efficiency and security−
NICT NEWS, Vol.2019.2, No.474, pp.13, 2019.
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.
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.
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.
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.
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.

Other Works

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.

Awards

Le Trieu Phong, Yoshinori Aono, Takuya Hayashi, Lihua Wang, and Shiho Moriai
IEEE Signal Processing Society, 2023 Best Paper Awards
"Privacy-Preserving Deep Learning via Additively Homomorphic Encryption"
Yuji Koike, Takuya Hayashi, and Takanori Isobe
14th International Workshop on Security (IWSEC 2019), Best Poster Awards
"A Practical Leakage-Resilient Scheme using Big-key Encryptions"

Organizing Activities

IEEE Cyber Science and Technology Congress (CyberSciTech) Program Committee
2019
International Workshop on Security (IWSEC) Local Organizing Committee
2016-2018
International Symposium on Computing and Networking (CANDAR) Program Committee
2016-2017
International Workshop on Information and Communication Security (WICS) Program Committee
2016-2017
ACM Symposium on Information, Computer and Communications Security (ASIACCS) Local Organizing Committee
2014