I am a researcher at NTT, Japan. My main research area is cryptography.

Bio.

• Apr. 2017-present: Researcher at NTT
• Mar. 2017 Ph.D of Science from The University of Tokyo (Supervisor: Prof. Noboru Kunihiro)
• Apr. 2014-Mar. 2017: JSPS Research Fellowship for Young Scientists (DC1)
• Apr. 2016-Mar. 2017 Collaborative Researcher at National Institute of Advanced Industrial Science and Technology (AIST)
• Mar. 2014 Master of Science from The University of Tokyo (Supervisor: Prof. Noboru Kunihiro)
• Aug. 2012-Mar. 2014: Technical Staff at National Institute of Advanced Industrial Science and Technology (AIST)
• Mar. 2012 Bachelor of Science from The University of Tokyo (Major: Mathematics)

Publications

International Conferences

• 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.)
• Constrained PRFs for NC1 in Traditional Groups. Nuttapong Attrapadung, Takahiro Matsuda, Ryo Nishimaki, Shota Yamada, Takashi Yamakawa CRYPTO 2018.
• Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model. Tsunekazu Saito, Keita Xagawa, Takashi Yamakawa EUROCRYPT 2018.
• Generalized Hardness Assumption for Self-bilinear Map with Auxiliary Information. Takashi Yamakawa, Goichiro Hanaoka, Noboru Kunihiro ACISP 2016.
• Adversary-Dependent Lossy Trapdoor Function from Hardness of Factoring Semi-smooth RSA Subgroup Moduli. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro CRYPTO 2016.
• A Short Fail-Stop Signature Scheme from Factoring. Takashi Yamakawa, Nobuaki Kitajima, Takashi Nishide, Goichiro Hanaoka, Eiji Okamoto 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 SCN 2014.
• Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro CRYPTO 2014. (Invited to Algorithmica.)
• Reducing Public Key Sizes in Bounded CCA-Secure KEMs with Optimal Ciphertext Length. Takashi Yamakawa, Shota Yamada, Takahiro Matsuda, Goichiro Hanaoka, Noboru Kunihiro 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 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 AsiaPKC 2013.

Journal Articles

• Self-Bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications. Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, Noboru Kunihiro Algorithmica 79(4).
• 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 IEICE Transactions 100-A(9).
• Efficient Key Encapsulation Mechanisms with Tight Security Reductions to Standard Assumptions in the Two Security Models. Yoshikazu Hanatani, Goichiro Hanaoka, Takahiro Matsuda, Takashi Yamakawa Security and Communication Networks 9(12).

Posters

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

Talks

• Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model.
  • ISEC Seminar, Jul. 2018
• Towards Ideal Self-bilinear Map.
  • The 5th ACM ASIA Public-Key Cryptography Workshop, Jun. 2018
• Constrained PRFs for NC1 in Traditional Groups.
  • Tokyo Crypto Day, March. 2018
  • ISEC Seminar, Sep. 2018
• Adversary-dependent Lossy Trapdoor Function from Hardness of Factoring Semi-smooth RSA Subgroup Moduli.
  • ISEC Seminar, Dec. 2016
  • 10-th Workshop on Secure Constructions and Applications of Public Key Cryptography, Feb. 2017
• Applications of Indistinguishability Obfuscation.
  • IEICE General Conference, Mar. 2015
• Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications.
  • ISEC Seminar, Dec. 2014
  • 8-th Workshop on Secure Constructions and Applications of Public Key Cryptography, Feb. 2015.
• Chosen Ciphertext Secure Encryption over Semi-smooth Subgroup Revisited.
  • IWSEC 2013, Nov. 2013

Awards

• Dean's Award for Outstanding Achievement from Graduate School of Frontier Science (Ph.D), The University of Tokyo, March 2017.
• Tsujii Shigeo Security Student Award, 2015.
• Dean's Award for Outstanding Achievement from Graduate School of Frontier Science (Master), The University of Tokyo, March 2014.
• SCIS Paper Award at SCIS 2013.
• IWSEC 2012 Best Poster Award.