Takashi Yamakawa
(山川高志)


I am a research scientist at NTT, Japan. My main research area is (post-quantum) cryptography.

Current Position

  • Distinguished Researcher at NTT Social Informatics Laboratories (formerly Secure Platform Laboratories)

  • Affiliate Associate Professor at Yukawa Institute for Theoretical Physics, Kyoto University

Experience

  • Jan. 2020-Apr. 2021: Visiting Associate Research Scholar at Princeton University (hosted by Prof. Mark Zhandry)

  • Apr. 2016-Mar. 2017 Collaborative Researcher at National Institute of Advanced Industrial Science and Technology (AIST)

  • Apr. 2014-Mar. 2017: JSPS Research Fellowship for Young Scientists (DC1)

  • Aug. 2014-Sep. 2014: Internship at NTT Secure Platform Laboratories (Mentor: Ryo Nishimaki)

  • Aug. 2012-Mar. 2014: Technical Staff at National Institute of Advanced Industrial Science and Technology (AIST)

Education

  • Apr. 2014-Mar. 2017 Ph.D in Science, The University of Tokyo (Supervisor: Prof. Noboru Kunihiro)

  • Apr. 2012-Mar. 2014 Master of Science, The University of Tokyo (Supervisor: Prof. Noboru Kunihiro)

  • Apr. 2008-Mar. 2012 Bachelor of Science, The University of Tokyo (Major: Mathematics)

Publications

See also DBLP and Google Scholar

The order of authors is alphabetical, unless otherwise noted.
(Most works done in 2016 or earlier use non-alphabetical order, and the others use alphabetical order. )

Preprint

International Conferences

Journal Articles

  • Compact Designated Verifier NIZKs from the CDH Assumption without Pairings. Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Journal of Cryptology, to be published, 2021 (merged full version of ePrint and ePrint)

  • Tighter Security Proofs for GPV-IBE in the Quantum Random Oracle Model. Shuichi Katsumata, Shota Yamada, Takashi Yamakawa, Journal of Cryptology, Volume 34, 2021. ePrint

  • Generic Hardness of Inversion on Ring and Its Relation to Self-Bilinear Map. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), Theoretical Computer Science 820, 2020 ePrint

  • Self-Bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order) Algorithmica 79(4), 2017. ePrint

  • Partially Wildcarded Ciphertext-Policy Attribute-Based Encryption and Its Performance Evaluation. Go Ohtake, Kazuto Ogawa, Goichiro Hanaoka, Shota Yamada, Kohei Kasamatsu, Takashi Yamakawa, Hideki Imai (non-alphabetical order) IEICE Transactions 100-A(9), 2017.

  • Efficient Key Encapsulation Mechanisms with Tight Security Reductions to Standard Assumptions in the Two Security Models. Yoshikazu Hanatani, Goichiro Hanaoka, Takahiro Matsuda, Takashi Yamakawa (non-alphabetical order), Security and Communication Networks 9(12), 2016.

Posters

  • A Black-Box Approach to Post-Quantum Zero-Knowledge in Constant Rounds. Nai-Hui Chia, Kai-Min Chung, Takashi Yamakawa, QIP 2021 (online)

  • Bounded CCA-Secure KEM from the Computational Bilinear Diffie-Hellman Assumption. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order) IWSEC 2012. (Best Poster Award)

Talks

  • Quantum commitments and signatures without one-way functions.

    • Ben-Gurion University CS Seminar, online, May 2022

  • On the Impossibility of Post-Quantum Black-Box Zero-Knowledge in Constant Rounds

  • Classical vs Quantum Random Oracles.

  • On Post-Quantum Black-Box Zero-Knowledge in Constant Rounds

  • A Black-Box Approach to Post-Quantum Zero-Knowledge in Constant Rounds

  • Classical Verification of Quantum Computations with Efficient Verification

  • NIZK from SNARG

    • TCC 2020, online, November 2020.

    • UC Berkeley Crypto Seminar, online, August 2020.

  • Adaptively Secure Constrained Pseudorandom Functions in the Standard Model.

    • CRYPTO 2020, online, August 2020.

  • Introduction to post-quantum public key cryptography and zero-knowledge. (耐量子公開鍵暗号入門・耐量子ゼロ知識証明入門)

    • The 3rd YITP Quantum Information School (第三回基研量子情報スクール), online, July 2020. (In Japanese)

  • Finding Collisions in a Quantum World: Quantum Black-Box Separation of Collision-Resistance and One-Wayness.

  • Adaptively Single-key Secure Constrained PRFs for NC1.

    • PKC 2019, Beijing, April 2019

  • Leakage-Resilient Identity-Based Encryption in Bounded Retrieval Model with Nearly Optimal Leakage-Ratio.

    • PKC 2019, Beijing, April 2019

  • Towards Ideal Self-bilinear Map.

    • The 5th ACM ASIA Public-Key Cryptography Workshop, June 2018 (Invited)

  • Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model.

    • Eurocrypt 2018, Tel Aviv, May 2018

    • ISEC Seminar, Sapporo, July 2018 (In Japanese)

  • Constrained PRFs for NC1 in Traditional Groups.

    • Tokyo Crypto Day, Tokyo, March. 2018

    • CRYPTO 2018, Santa Barbara, Aug. 2018

    • ISEC Seminar, Tokyo, Sep. 2018 (In Japanese)

  • Adversary-dependent Lossy Trapdoor Function from Hardness of Factoring Semi-smooth RSA Subgroup Moduli.

    • CRYPTO 2016, Santa Barbara, Aug. 2016

    • ISEC Seminar, Hiroshima, Dec. 2016 (In Japanese)

    • 10-th Workshop on Secure Constructions and Applications of Public Key Cryptography, Tokyo, Feb. 2017 (In Japanese)

  • Generalized Hardness Assumption for Self-bilinear Map with Auxiliary Information.

    • ACISP 2016, Melbourne, July 2016

  • Applications of Indistinguishability Obfuscation. (識別不可性難読化の応用)

    • IEICE General Conference, Shiga, Mar. 2015 (In Japanese)

  • A Short Fail-Stop Signature Scheme from Factoring.

    • ProvSec 2014, Hong Kong, Oct. 2014

  • Chosen Ciphertext Security on Hard Membership Decision Groups: The Case of Semi-smooth Subgroups.

    • SCN 2014, Amalfi, Sep. 2014

  • Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications.

    • CRYPTO 2014, Santa Barbara, Aug. 2014

    • ISEC Seminar, Tokyo, Dec. 2014 (In Japanese)

    • 8-th Workshop on Secure Constructions and Applications of Public Key Cryptography, Tokyo, Feb. 2015 (In Japanese)

  • Reducing Public Key Sizes in Bounded CCA-Secure KEMs with Optimal Ciphertext Length.

    • ISC 2013, Dallas, Nov. 2013

  • Chosen Ciphertext Secure Encryption over Semi-smooth Subgroup Revisited.

    • IWSEC 2013, SCIS/CSS Invited Session, Okinawa, Nov. 2013 (Invited)


Lectures

Fall 2021, YITP Intensive Lecture 1 (on (quantum) cryptography) , Yukawa Institute of Theoretical Physics, Kyoto University (In Japanese)

Activities

Program Committee Member: Asiacrypt 2021, APKC 2019, APKC 2018

Subreviewer : Asiacrypt, CRYPTO, Eurocrypt, PKC, TCC, ACISP, ACNS, ISITA, IWSEC, Provsec, SCN, etc.


Awards

  • Asiacrypt 2020 Best Paper Award

    • for the paper: Finding Collisions in a Quantum World: Quantum Black-Box Separation of Collision-Resistance and One-Wayness (with Akinori Hosoyamada).

  • Dean's Award for Outstanding Achievement from Graduate School of Frontier Science (Ph.D) (top honor in the department), The University of Tokyo, March 2017.

  • Tsujii Shigeo Security Student Award, 2015.

    • for the paper: Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications (with Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro, CRYPTO 2014).

  • Dean's Award for Outstanding Achievement from Graduate School of Frontier Science (Master) (top honor in the department), The University of Tokyo, March 2014.

  • SCIS Paper Award at SCIS 2013 (Japanese domestic conference).

    • for the paper: 素因数分解問題に基づくSemi-smooth部分群上のCCA安全な公開鍵暗号の安全性証明について (On Security Proof of CCA-Secure Public Key Encryption in Semi-Smooth Subgroups) (with Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro)

  • IWSEC 2012 Best Poster Award.

    • for the poster: Bounded CCA-Secure KEM from the Computational Bilinear Diffie-Hellman Assumption (with Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro)


Hobbies

  • Othello: A two-player strategy board game popular in Japan, I've been playing since 2002. I'm currently ranked 5th at World Othello Federation Ratings (Apr. 2020).
    You can learn the rule and basic strategies from a free e-book written by a former world champion Brian Rose here.

  • I'm also a fan of other board games including Go, Shogi (Japanese Chess), Backgammon etc.

Contact Information

Please send official invitation emails (PC member, talks, etc. ) to: takashi.yamakawa.ga@hco.ntt.co.jp

For other emails (review request, question/comment on paper, etc.): takashi.yamakawa.obf@gmail.com