National Institute of Advanced Industrial Science and Technology (AIST)
Cyber Physical Security Research Center (CPSEC)
Senior Researcher
Interests: Secure Multiparty Computation, Public-key Cryptosystems
e-mail：ohara.kazuma [at] aist.go.jp
2020.01-present: National Institute of Advanced Industrial Science and Technology
Researcher @ Cyber Physical Security Research Center
2014.04-2019.12: NEC Corporation
Researcher @ Central Research Laboratories
2012.9-2014.03: National Institute of Advanced Industrial Science and Technology
Technical Staff @ Research Institute for Secure Systems
2019.09: Ph.D. in Engineering from Department of Informatics, Graduate School of Informatics and Engineering, The University of Electro-Communications
Dissertation: Efficient Constructions and Implementations for Secure Multi-Party Computation
Supervisor: Prof. Mitsugu Iwamoto
2014.03: M.S. in Engineering from Department of Informatics, Graduate School of Informatics and Engineering, The University of Electro-Communications
Supervisor: Prof. Kazuo Ohta (Currently Professor Emeritus at The University of Electro-Communications)
2012.03: B.S. in Engineering from Department of Communication Engineering and Informatics, Faculty of Informatics and Engineering, The University of Electro-Communications
Multi-Party Computation for Modular Exponentiation based on Replicated Secret Sharing
Kazuma Ohara, Yohei Watanabe, Mitsugu Iwamoto, Kazuo Ohta
IEICE Transactions, Vol.E102-A, No.9, pp.1079-1090, 2019.
Shortening the Libert-Peters-Yung Revocable Group Signature Scheme by Using the Random Oracle Methodology
Kazuma Ohara, Keita Emura, Goichiro Hanaoka, Ai Ishida, Kazuo Ohta, Yusuke Sakai.
IEICE Transactions, Vol. E102-A, No.9, pp.1101-1117, 2019. [eprint]
Group Signatures with Message-Dependent Opening: Formal Definitions and Constructions
Keita Emura, Goichiro Hanaoka, Yutaka Kawai, Takahiro Matsuda, Kazuma Ohara, Kazumasa Omote, Yusuke Sakai
Security and Communication Networks 2019: 4872403:1-4872403:36, 2019.
Secure Parallel Computation on Privately Partitioned Data and Applications
Nuttapong Attrapadung, Hiraku Morita, Kazuma Ohara, Jacob C. N. Schuldt, Tadanori Teruya, Kazunari Tozawa.
ACM CCS 2022, pp.151-164.
Efficient Two-party Exponentiation from Quotient Transfer
Yi Lu, Keisuke Hara, Kazuma Ohara, Jacob C. N. Schuldt, Keisuke Tanaka.
ACNS 2022, pp.643-662.
Memory and Round-Efficient MPC Primitives in the Pre-Processing Model from Unit Vectorization
Nuttapong Attrapadung, Hiraku Morita, Kazuma Ohara, Jacob C. N. Schuldt, Kazunari Tozawa.
ACM ASIACCS 2022, pp.858-872.
Efficient Dynamic Searchable Encryption with Forward Privacy under the Decent Leakage
Yohei Watanabe, Kazuma Ohara, Mitsugu Iwamoto, Kazuo Ohta.
CODASPY 2022, pp.312-323.
Non-Interactive Secure Multiparty Computation for Symmetric Functions, Revisited: More Efficient Constructions and Extensions
Reo Eriguchi, Kazuma Ohara, Shota Yamada, Koji Nuida.
CRYPTO 2021, pp.305-334.
Oblivious Linear Group Actions and Applications
Nuttapong Attrapadung, Goichiro Hanaoka, Takahiro Matsuda, Hiraku Morita, Kazuma Ohara, Jacob C. N. Schuldt, Tadanori Teruya, Kazunari Tozawa.
ACM CCS 2021, pp.630-650.
Revisiting Fuzzy Signatures: Towards a More Risk-Free Cryptographic Authentication System based on Biometrics
Shuichi Katsumata, Takahiro Matsuda, Kazuma Ohara, Kenta Takahashi, Wataru Nakamura.
ACM CCS 2021, pp.2046-2065.
Secure Graph Analysis at Scale
Toshinori Araki, Jun Furukawa, Kazuma Ohara, Benny Pinkas, Hanan Rosemarin, Hikaru Tsuchida.
ACM CCS 2021, pp.610-629.
Semantic Definition of Anonymity in Identity-Based Encryption and Its Relation to Indistinguishability-Based Definition
Goichiro Hanaoka, Misaki Komatsu, Kazuma Ohara, Yusuke Sakai, Shota Yamada.
ESORICS 2020, pp.65-85.
Generalizing the SPDZ Compiler For Other Protocols
Toshinori Araki, Assi Barak, Jun Furukawa, Marcel Keller, Yehuda Lindell, Kazuma Ohara, Hikaru Tsuchida.
ACM CCS 2018, pp.880-895. [eprint]
Optimized Honest-Majority MPC for Malicious Adversaries – Breaking the 1 Billion-Gate Per Second Barrier
Toshinori Araki, Assi Barak, Jun Furukawa, Yehuda Lindell, Ariel Nof, Kazuma Ohara.
IEEE S&P 2017, pp.843-862.
High-Throughput Semi-Honest Secure Three-Party Computation with an Honest Majority
Toshinori Araki, Jun Furukawa, Yehuda Lindell, Ariel Nof, Kazuma Ohara.
ACM CCS 2016, pp.805-817. [eprint]
Constant Rounds Almost Linear Complexity Multi-party Computation for Prefix Sum
Kazuma Ohara , Kazuo Ohta, Koutarou Suzuki, Kazuki Yoneyama.
AFRICACRYPT 2014, pp.285-299.
Privacy-preserving smart metering with verifiability for both billing and energy management
Kazuma Ohara, Yusuke Sakai, Fumiaki Yoshida, Mitsugu Iwamoto, Kazuo Ohta.
AsiaPKC@AsiaCCS 2014, pp.23-32
A Group Signature Scheme with Unbounded Message-Dependent Opening
Kazuma Ohara, Yusuke Sakai, Keita Emura, Goichiro Hanaoka.
AsiaCCS 2013, pp.517-522.
How to Make a Secure Index for Searchable Symmetric Encryption, Revisited
Yohei Watanabe, Takeshi Nakai, Kazuma Ohara, Takuya Nojima, Yexuan Liu, Mitsugu Iwamoto, Kazuo Ohta.
IACR Cryptol. ePrint Arch. 2021: 948 (2021).
Generalizing the SPDZ Compiler For Other Protocols
Toshinori Araki, Assi Barak, Jun Furukawa, Marcel Keller, Yehuda Lindell, Kazuma Ohara, Hikaru Tsuchida.
IACR Cryptol. ePrint Arch. 2018: 762 (2018)
Shortening the Libert-Peters-Yung Revocable Group Signature Scheme by Using the Random Oracle Methodology
Kazuma Ohara, Keita Emura, Goichiro Hanaoka, Ai Ishida, Kazuo Ohta, Yusuke Sakai.
IACR Cryptol. ePrint Arch. 2016: 477 (2016)
High-Throughput Semi-Honest Secure Three-Party Computation with an Honest Majority
Toshinori Araki, Jun Furukawa, Yehuda Lindell, Ariel Nof, Kazuma Ohara.
IACR Cryptol. ePrint Arch. 2016: 768 (2016)
Optimized Honest-Majority MPC for Malicious Adversaries - Breaking the 1 Billion-Gate Per Second Barrier
Workshop on Cryptographic Technologies for Securing Network Storage and Their Mathematical Modeling, June 13, 2017.
A Compact Revocable Group Signature Scheme with Scalability
International Workshop on Security 2014 (IWSEC 2014), August 27, 2014.
How to Choose Suitable Secure Multiparty Computation Using Generalized SPDZ
Toshinori Araki, Assi Barak, Jun Furukawa, Marcel Keller, Kazuma Ohara, Hikaru Tsuchida
ACM CCS 2018, pp.2198-2200.
DEMO: High-Throughput Secure Three-Party Computation of Kerberos Ticket Generation
Toshinori Araki, Assi Barak, Jun Furukawa, Yehuda Lindell, Kazuma Ohara
ACM CCS 2016, pp.1841-1843.
An t-Resilient Unconditionally Secure First-Price Auction Protocol
Kazuma Ohara, Yusuke Sakai, Mitsugu Iwamoto, Kazuo Ohta
International Workshop on Security 2012 (IWSEC 2012)．
“Secure Computation” - Introduction to Advanced Cryptography - Fundamentals, Applications, and Development Issues of Cryptography Transformed with Quantum Computers - R2
Kanagawa Institute of Industrial Science and Technology (KISTEC), hosted virtually, 2020.10.
Meguro-Kai Award (Outstanding Student Award) of The University of Electro-Communications (2011.03)
SCIS2014 Paper Award (2014.01)
ACM CCS2016 Best Paper Award (2016.10)
CSS2019 Encouragement Research Award (2019.10)
CSS2020 Encouragement Research Award (2020.10)
CSS2022 Outstanding Paper Award (2022.10)