Kazuma Ohara

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

Work Experience

  • 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

Education

  • 2019.09: Ph.D. in Engineering from Department of Informatics, Graduate School of Informatics and Engineering, The University of Electro-Communications

  • 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

Journal Articles (Refereed)

  • 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.

International Conference (Refereed)

  • 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.

Preprint

  • 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)

Invited Talks (in English)

  • 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.

Posters

  • 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)．

Awards

Activities