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)

• Oct. 2021-present: 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

• Quantum Public-Key Encryption with Tamper-Resilient Public Keys from One-Way Functions. Fuyuki Kitagawa, Tomoyuki Morimae, Ryo Nishimaki, Takashi Yamakawa arXiv ePrint

• Classical vs Quantum Advice and Proofs under Classically-Accessible Oracle. Xingjian Li,  Qipeng Liu,  Angelos Pelecanos, Takashi Yamakawa arXiv

• Quantum Advantage from One-Way Functions. Tomoyuki Morimae, Takashi Yamakawa arXiv ePrint

• One-Wayness in Quantum Cryptography. Tomoyuki Morimae, Takashi Yamakawa, arXiv, ePrint

• Certified Everlasting Secure Collusion-Resistant Functional Encryption, and More. Taiga Hiroka, Fuyuki Kitagawa Tomoyuki Morimae, Ryo Nishimaki, Tapas Pal, Takashi Yamakawa arXiv ePrint
  (Preliminary version appeared as Certified Everlasting Functional Encryption. arXiv)

International Conferences

• Publicly Verifiable Deletion from Minimal Assumptions.  Fuyuki Kitagawa, Ryo Nishimaki, Takashi Yamakawa, arXiv ePrint TCC 2023

• Quantum Complexity for Discrete Logarithms and Related Problems. Minki Hhan, Takashi Yamakawa, Aaram Yun, arXiv, ePrint AQIS 2023 (long talk)

• A New Approach to Post-Quantum Non-Malleability. Xiao Liang, Omkant Pandey, Takashi Yamakawa, arXiv, ePrint FOCS 2023

• Obfuscation of Pseudo-Deterministic Quantum Circuits. James Bartusek,  Fuyuki Kitagawa, Ryo Nishimaki, Takashi Yamakawa, STOC 2023 arXiv, ePrint

• Public Key Encryption with Secure Key Leasing.  Shweta Agrawal, Fuyuki Kitagawa, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Eurocrypt 2023 arXiv, ePrint 

• From the Hardness of Detecting Superpositions to Cryptography: Quantum Public Key Encryption and Commitments. Minki Hhan, Tomoyuki Morimae, Takashi Yamakawa, Eurocrypt 2023, QCW 2022, QIP 2023, AQIS 2023 arXiv, ePrint video (by Minki Hhan)

• Proofs of Quantumness from Trapdoor Permutations.  Tomoyuki Morimae, Takashi Yamakawa, ITCS 2023, QCW 2022 arXiv, ePrint  video (by Tomoyuki Morimae)

• Bounded Functional Encryption for Turing Machines: Adaptive Security from General Assumptions. Shweta Agrawal, Fuyuki Kitagawa, Anuja Modi,  Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, TCC 2022 ePrint video (by Anuja Modi)

• Classically Verifiable NIZK for QMA with Preprocessing. Tomoyuki Morimae, Takashi Yamakawa, Asiacrypt 2022 ePrint arXiv video

• Verifiable Quantum Advantage without Structure. Takashi Yamakawa, Mark Zhandry, FOCS 2022, QIP 2023 (plenary talk) arXiv, ePrint quanta magazine video1 video2 (by Mark Zhandry)

• Quantum commitments and signatures without one-way functions. Tomoyuki Morimae, Takashi Yamakawa, CRYPTO 2022, QCW2022, QIP 2023 arXiv ePrint  video

• Post-Quantum Simulatable Extraction with Minimal Assumptions: Black-Box and Constant-Round. Nai-Hui Chia, Kai-Min Chung, Xiao Liang, Takashi Yamakawa, CRYPTO 2022 arXiv ePrint video (by Xiao Liang)

• Certified Everlasting Zero-Knowledge Proof for QMA. Taiga Hiroka, Tomoyuki Morimae, Ryo Nishimaki, Takashi Yamakawa, CRYPTO 2022, QIP 2022 (merged short plenary talk), QCRYPT 2022 arXiv ePrint  video (by Taiga Hiroka)

• Secure Software Leasing from Standard Assumptions. Fuyuki Kitagawa,  Ryo Nishimaki, Takashi Yamakawa, TCC2021,  arXiv  ePrint video (by Ryo Nishimaki)

• On the Impossibility of Post-Quantum Black-Box Zero-Knowledge in Constant Rounds. Nai-Hui Chia, Kai-Min Chung, Qipeng Liu, Takashi Yamakawa, FOCS 2021, QCRYPT 2021 (merged), QIP 2022 (merged) arXiv  ePrint video

• Quantum Encryption with Certified Deletion Revisited: Public Key, Attribute-Based, and Classical Communication Taiga Hiroka, Tomoyuki Morimae, Ryo Nishimaki, Takashi Yamakawa, Asiacrypt 2021, QCRYPT2021, QIP 2022 (merged short plenary talk)  arXiv  ePrint video (by Taiga Hiroka)
  (Preliminary version appeared as Quantum Encryption with Certified Deletion: Public Key and Attribute-Based ePrint )

• A Black-Box Approach to Post-Quantum Zero-Knowledge in Constant Rounds. Nai-Hui Chia, Kai-Min Chung, Takashi Yamakawa, CRYPTO 2021, QCRYPT 2021 (merged), QIP 2022 (merged) arXiv ePrint video

• Round-Optimal Blind Signatures in the Plain Model from Classical and Quantum Standard Assumptions. Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Eurocrypt 2021.  ePrint video (by Ryo Nishimaki)

• Classical vs Quantum Random Oracles.  Takashi Yamakawa, Mark Zhandry, Eurocrypt 2021. ePrint video
  (Preliminary version appeared as A Note on Separating Classical and Quantum Random Oracles. ePrint)

• Adaptively Secure Inner Product Encryption from LWE.  Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Asiacrypt 2020. ePrint video (by Shota Yamada) 

• Finding Collisions in a Quantum World: Quantum Black-Box Separation of Collision-Resistance and One-Wayness.  Akinori Hosoyamada, Takashi Yamakawa, Asiacrypt 2020. (Best Paper Award) ePrint video (by Akinori Hosoyamada) 

• NIZK from SNARG. Fuyuki Kitagawa, Takahiro Matsuda, Takashi Yamakawa, TCC 2020. ePrint  video

• Classical Verification of Quantum Computations with Efficient Verifier. Nai-Hui Chia, Kai-Min Chung, Takashi Yamakawa, TCC 2020. arXiv ePrint video (by Nai-Hui Chia)   

• Adaptively Secure Constrained Pseudorandom Functions in the Standard Model. Alex Davidson, Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, CRYPTO 2020. ePrint  video 

• Compact NIZKs from Standard Assumptions on Bilinear Maps.  Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Eurocrypt 2020.  ePrint  video (by Shuichi Katsumata) 

• Quantum Random Oracle Model with Auxiliary Input. Minki Hhan, Keita Xagawa, Takashi Yamakawa, Asiacrypt 2019.  ePrint

• Adaptively Secure and Succinct Functional Encryption: Improving Security and Efficiency, Simultaneously. Fuyuki Kitagawa, Ryo Nishimaki , Keisuke Tanaka, Takashi Yamakawa, CRYPTO 2019. ePrint 

• Exploring Constructions of Compact NIZKs from Various Assumptions.  Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, CRYPTO 2019.  ePrint video (by Shuichi Katsumata) 

• Designated Verifier/Prover and Preprocessing NIZKs from Diffie-Hellman Assumptions. Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Eurocrypt 2019. ePrint  video (by Shuichi Katsumata) 

• (Tightly) QCCA-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model. Keita Xagawa, Takashi Yamakawa, PQCrypto 2019. ePrint

• Leakage-resilient Identity-based Encryption in Bounded Retrieval Model with Nearly Optimal Leakage-Ratio. Ryo Nishimaki, Takashi Yamakawa, PKC 2019. ePrint

• Adaptively Single-key Secure Constrained PRFs for NC1. Nuttapong Attrapadung, Takahiro Matsuda, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, PKC 2019. ePrint

• Tighter Security Proofs for GPV-IBE in the Quantum Random Oracle Model.   Shuichi Katsumata, Shota Yamada, Takashi Yamakawa, Asiacrypt 2018. (Invited to Journal of Cryptology.) ePrint

• Constrained PRFs for NC1 in Traditional Groups.   Nuttapong Attrapadung, Takahiro Matsuda, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, CRYPTO 2018.  ePrint  video

• Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model.  Tsunekazu Saito, Keita Xagawa, Takashi Yamakawa, Eurocrypt 2018. ePrint

• Generalized Hardness Assumption for Self-bilinear Map with Auxiliary Information.  Takashi Yamakawa, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), ACISP 2016. 

• Adversary-Dependent Lossy Trapdoor Function from Hardness of Factoring Semi-smooth RSA Subgroup Moduli. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), CRYPTO 2016. ePrint video 

• A Short Fail-Stop Signature Scheme from Factoring.   Takashi Yamakawa, Nobuaki Kitajima, Takashi Nishide, Goichiro Hanaoka, Eiji Okamoto (non-alphabetical order), ProvSec 2014. 

• Chosen Ciphertext Security on Hard Membership Decision Groups: The Case of Semi-smooth Subgroups of Quadratic Residues.   Takashi Yamakawa, Shota Yamada, Koji Nuida, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), SCN 2014. 

• Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications.   Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), CRYPTO 2014. (Invited to Special Issues of Algorithmica.) ePrint video 

• Reducing Public Key Sizes in Bounded CCA-Secure KEMs with Optimal Ciphertext Length.   Takashi Yamakawa, Shota Yamada, Takahiro Matsuda, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), ISC 2013. 

• Partially Wildcarded Attribute-based Encryption and Its Efficient Construction.    Go Ohtake, Yuki Hironaka, Kenjiro Kai, Yosuke Endo, Goichiro Hanaoka, Hajime Watanabe, Shota Yamada, Kohei Kasamatsu, Takashi Yamakawa, Hideki Imai (non-alphabetical order), SECRYPT 2013. 

• Efficient Variants of the Naor-Yung and Dolev-Dwork-Naor Transforms for CCA Secure Key Encapsulation Mechanism.  Takashi Yamakawa, Shota Yamada, Takahiro Matsuda, Goichiro Hanaoka, Noboru Kunihiro (non-alphabetical order), AsiaPKC 2013. 

Journal Articles

• NIZK from SNARGs. Fuyuki Kitagawa, Takahiro Matsuda, Takashi Yamakawa, Journal of Cryptology,  2023,  ePrint

• Compact Designated Verifier NIZKs from the CDH Assumption without Pairings.  Shuichi Katsumata, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa, Journal of Cryptology, Volume 34,  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

• Classically Verifiable (Dual-mode) NIZK for QMA with Preprocessing. Tomoyuki Morimae, Takashi Yamakawa, QCrypt 2021 (online) 

• 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 Advantage and Cryptography

  • 6th Kanazawa Angou-Riron-Benkyou-Kai, Kanazawa, Aug. 2023

• Classical vs Quantum Advice and Proofs under Classically-Accessible Oracle

  • YITP Seminar, Kyoto, Jul. 2023

• Quantum Advantage from Cryptographic Assumptions

  • 2023 EWHA-KMS International Workshop on Cryptography, Seoul, Jul. 2023

• Quantum Public-Key Encryption with Tamper-Resilient Public Keys from One-Way Functions

  • QIT 48, Kyoto, May. 2023

• Non-uniformity and Quantum Advice in the Quantum Random Oracle Model  (proxy for Qipeng Liu)

  • Eurocrypt 2023, Lyon, Apr. 2023

• Classically Verifiable NIZK for QMA with Preprocessing

  • Asiacrypt 2022, Taipei, Dec. 2022

• Proofs of Quantumness from Trapdoor Permutations

  • QCW 2022, Taipei, Dec. 2022

• Verifiable Quantum Advantage Without Structure

  • Theory Seminar, Taipei, May 2023

  • CS Seminar at CQT, online, May 2023

  • QIP 2023, Ghent, Jan. 2023

  • FOCS 2022, Denver, Nov. 2022

  • Third Kyoto Workshop on Quantum Information, Computation, and Foundations, online, Oct. 2022 

• Recent Devolpments in Complexity-based Quantum Cryptography

  • Mathematics of Post-Quantum Cryptography and Quantum Information, Fukuoka, Aug. 2022  video (In Japanese) 

• Quantum commitments and signatures without one-way functions

  • CRYPTO 2022, Santa Barbara, Aug. 2022

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

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

  • FOCS 2021, online, Feb. 2022

• Quantum Computation and Cryptography

  • Information Mathematics Seminar, the University of Tokyo, Tokyo, Dec. 2022 (in Japanese)

  • ISEC Seminar, online, Nov. 2022  (in Japanese)

  • YITP Seminar, online, Dec. 2021 (in Japanese)

• Classical vs Quantum Random Oracles.

  • ENS de Lyon,  RHUL, and CWI Joint Online Crypto Seminar, online, Mar. 2022

  • Eurocrypt 2021, online, Dec. 2021 

  • Workshop on Cryptography and Information Security 2021, online, Sep. 2021 (In Japanese)

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

  • Second Kyoto Workshop on Quantum Information, Computation, and Foundation, online, Sep. 2021

  • QCRYPT 2021, online, Aug. 2021

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

  • CRYPTO 2021, online, Aug. 2021

• Classical Verification of Quantum Computations with Efficient Verification

  • QIT 44, online, May 2021

• 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.

  • The 3rd YITP Quantum Information School, online, July 2020. (In Japanese) 

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

  • ENS de Lyon,  RHUL, and CWI Joint Online Crypto Seminar, online, July 2021

  • Joint Workshop of NTT Labs (Japan) and NTT Research (USA), Kyoto, December 2019.

  • Theory Day in Taiwan (2019), Taipei, October 2019.  

• 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.  

  • 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 2023, TCC2023, QCRYPT2023, ITC2023, TQC2023, QIP 2023, QCW 2022, Asiacrypt 2022, Asiacrypt 2021, APKC 2019, APKC 2018

Conference Subreview : Asiacrypt, CRYPTO, Eurocrypt, PKC, TCC,
                                                        ACISP, ACNS, FOCS, ISAAC, ISITA, ITC, ITCS, IWSEC, Provsec, SCN, STOC etc. 

Journal Review: Designs, Codes and Cryptography, Nature Physics, Quantum,  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 (July 2022).
  You can learn the rule and basic strategies from a free e-book written by a former world champion Brian Rose here. 

• Other board games including Go, Shogi (Japanese Chess), Backgammon etc.

• Listening to classical music and playing the piano.

• Learning languages.

Contact Information

takashi.yamakawa.obf@gmail.com
takashi.yamakawa@ntt.com
(The following email address also still works: takashi.yamakawa.ga@hco.ntt.co.jp )