Organization
School of Computing Visiting Professor
Title
Visiting Professor
External link
XAGAWA KEITA
Degree
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Doctor of Science ( 2010.3 Tokyo Institute of Technology )
Education
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Tokyo Institute of Technology Graduate School of Information Science and Engineering
2007.4 - 2010.3
Country： Japan
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Tokyo Institute of Technology Graduate School of Information Science and Engineering
2005.4 - 2007.3
Country： Japan
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Kyoto University
2000.4 - 2005.3
Country： Japan
Research History
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Technology Innovation Institute Cryptography Research Center
2023.5
Country：United Arab Emirates
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NTT
2010.4 - 2023.4
Country：Japan
Papers
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The Security of ML-DSA Against Fault-Injection Attacks Reviewed
Haruhisa Kosuge, Keita Xagawa
ASIACRYPT 2025, Part II 641 - 674 2025.12
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Post-Quantum Cryptographic Analysis of SSH. Reviewed
Benjamin Bencina, Benjamin Dowling, Varun Maram, Keita Xagawa
IEEE Symposium on Security and Privacy (SP) 595 - 613 2025.5
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Probabilistic Hash-and-Sign with Retry in the Quantum Random Oracle Model Reviewed
Haruhisa Kosuge, Keita Xagawa
Public-Key Cryptography – PKC 2024, Part I 259 - 288 2024.4
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Signatures with Memory-Tight Security in the Quantum Random Oracle Model. Reviewed
Keita Xagawa
EUROCRYPT 2024, Part VII 30 - 58 2024.4
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Multiple-Valued Plaintext-Checking Side-Channel Attacks on Post-Quantum KEMs Reviewed
Yutaro Tanaka, Rei Ueno, Keita Xagawa, Akira Ito, Junko Takahashi, Naofumi Homma
IACR Transactions on Cryptographic Hardware and Embedded Systems 2023 ( 3 ) 473 - 503 2023.6
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Post-quantum Anonymity of Kyber Reviewed
Varun Maram, Keita Xagawa
Public-Key Cryptography – PKC 2023 3 - 35 2023.5
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Curse of Re-encryption: A Generic Power/EM Analysis on Post-Quantum KEMs.
Rei Ueno, Keita Xagawa, Yutaro Tanaka, Akira Ito, Junko Takahashi, Naofumi Homma
IACR Transactions on Cryptographic Hardware and Embedded Systems 2022 ( 1 ) 296 - 322 2022
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Anonymity of NIST PQC Round 3 KEMs. Reviewed
Keita Xagawa
Advances in Cryptology - EUROCRYPT 2022 - 41st Annual International Conference on the Theory and Applications of Cryptographic Techniques 551 - 581 2022
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Fault-Injection Attacks Against NIST's Post-Quantum Cryptography Round 3 KEM Candidates.
Keita Xagawa, Akira Ito, Rei Ueno, Junko Takahashi, Naofumi Homma
Advances in Cryptology - ASIACRYPT 2021 - 27th International Conference on the Theory and Application of Cryptology and Information Security 33 - 61 2021
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Quantum algorithm for the multicollision problem.
Akinori Hosoyamada, Yu Sasaki, Seiichiro Tani, Keita Xagawa
Theoretical Computer Science 842 100 - 117 2020
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Non-committing Encryption with Constant Ciphertext Expansion from Standard Assumptions.
Yusuke Yoshida, Fuyuki Kitagawa, Keita Xagawa, Keisuke Tanaka
Advances in Cryptology - ASIACRYPT 2020 - 26th International Conference on the Theory and Application of Cryptology and Information Security 36 - 65 2020
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ModFalcon: Compact Signatures Based On Module-NTRU Lattices.
Chitchanok Chuengsatiansup, Thomas Prest, Damien Stehlé, Alexandre Wallet, Keita Xagawa
ASIA CCS '20: The 15th ACM Asia Conference on Computer and Communications Security(AsiaCCS) 853 - 866 2020
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Quantum Random Oracle Model with Auxiliary Input.
Minki Hhan, Keita Xagawa, Takashi Yamakawa
Advances in Cryptology - ASIACRYPT 2019 - 25th International Conference on the Theory and Application of Cryptology and Information Security 584 - 614 2019
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(Tightly) QCCA-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model.
Keita Xagawa, Takashi Yamakawa
Post-Quantum Cryptography - 10th International Conference(PQCrypto) 249 - 268 2019
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Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model.
Tsunekazu Saito, Keita Xagawa, Takashi Yamakawa
Advances in Cryptology - EUROCRYPT 2018 - 37th Annual International Conference on the Theory and Applications of Cryptographic Techniques 520 - 551 2018
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Cryptanalysis of Comparable Encryption in SIGMOD'16.
Caleb Horst, Ryo Kikuchi, Keita Xagawa
Proceedings of the 2017 ACM International Conference on Management of Data 1069 - 1084 2017
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Key-Private Proxy Re-Encryption from Lattices, Revisited.
Ryo Nishimaki, Keita Xagawa
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences 98-A ( 1 ) 100 - 116 2015
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Strongly secure authenticated key exchange from factoring, codes, and lattices.
Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, Kazuki Yoneyama
Designs, Codes and Cryptography 76 ( 3 ) 469 - 504 2015
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Nishanth Chandran, Melissa Chase, Feng-Hao Liu, Ryo Nishimaki, Keita Xagawa
Public-Key Cryptography - PKC 2014 - 17th International Conference on Practice and Theory in Public-Key Cryptography 95 - 112 2014
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Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, Kazuki Yoneyama
8th ACM Symposium on Information, Computer and Communications Security(AsiaCCS) 83 - 94 2013
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Improved (Hierarchical) Inner-Product Encryption from Lattices.
Keita Xagawa
Public-Key Cryptography - PKC 2013 - 16th International Conference on Practice and Theory in Public-Key Cryptography 235 - 252 2013
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Efficient Public Key Encryption Based on Ideal Lattices. Reviewed
Damien Stehlé, Ron Steinfeld, Keisuke Tanaka, Keita Xagawa
Advances in Cryptology - ASIACRYPT 2009, 15th International Conference on the Theory and Application of Cryptology and Information Security(ASIACRYPT) 617 - 635 2009
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Concurrently Secure Identification Schemes Based on the Worst-Case Hardness of Lattice Problems. Reviewed
Akinori Kawachi, Keisuke Tanaka, Keita Xagawa
Advances in Cryptology - ASIACRYPT 2008, 14th International Conference on the Theory and Application of Cryptology and Information Security(ASIACRYPT) 372 - 389 2008
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On the Efficiency of Generic, Quantum Cryptographic Constructions Reviewed
Keita Xagawa
IACR Communications in Cryptology 1 ( 1 ) 2024.4
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Chameleon Hashing Security Enhancement to Hierarchical Identity-Based Identification.
Atsushi Fujioka, Keisuke Saito, Taiichi Saito, Keita Xagawa
International Symposium on Information Theory and Its Applications(ISITA) 260 - 265 2024
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Making the Identity-Based Diffie-Hellman Key Exchange Efficiently Revocable. Reviewed
Kohei Nakagawa, Atsushi Fujioka, Akira Nagai, Junichi Tomida, Keita Xagawa, Kan Yasuda
LATINCRYPT 171 - 191 2023
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Cryptanalysis of Boyen's attribute-based encryption scheme in TCC 2013.
Shweta Agrawal, Rajarshi Biswas, Ryo Nishimaki, Keita Xagawa, Xiang Xie, Shota Yamada 0001
Designs, Codes and Cryptography 90 ( 10 ) 2301 - 2318 2022
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Keita Xagawa
Selected Areas in Cryptography - 28th International Conference(SAC) 47 - 67 2021
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Cryptanalysis of a rank-based signature with short public keys.
Nicolas Aragon, Olivier Blazy, Jean-Christophe Deneuville, Philippe Gaborit, Terry Shue Chien Lau, Chik How Tan, Keita Xagawa
Designs, Codes and Cryptography 88 ( 4 ) 643 - 653 2020
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Post-quantum Provably-Secure Authentication and MAC from Mersenne Primes.
Houda Ferradi, Keita Xagawa
Topics in Cryptology - CT-RSA 2020 - The Cryptographers' Track at the RSA Conference 2020(CT-RSA) 469 - 495 2020
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Improved Quantum Multicollision-Finding Algorithm.
Akinori Hosoyamada, Yu Sasaki, Seiichiro Tani, Keita Xagawa
Post-Quantum Cryptography - 10th International Conference(PQCrypto) 350 - 367 2019
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Accumulable optimistic fair exchange from verifiably encrypted homomorphic signatures.
Jae Hong Seo, Keita Emura, Keita Xagawa, Kazuki Yoneyama
International Journal of Information Security 17 ( 2 ) 193 - 220 2018
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Keita Xagawa
Post-Quantum Cryptography - 9th International Conference(PQCrypto) 142 - 161 2018
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Keita Xagawa
IACR Cryptology ePrint Archive 2018 831 - 831 2018
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Jonathan Bootle, Mehdi Tibouchi, Keita Xagawa
Topics in Cryptology - CT-RSA 2018 - The Cryptographers' Track at the RSA Conference 2018(CT-RSA) 80 - 97 2018
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Quantum Multicollision-Finding Algorithm.
Akinori Hosoyamada, Yu Sasaki, Keita Xagawa
Advances in Cryptology - ASIACRYPT 2017 - 23rd International Conference on the Theory and Applications of Cryptology and Information Security 179 - 210 2017
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Public-Key Cryptosystems Resilient to Continuous Tampering and Leakage of Arbitrary Functions.
Eiichiro Fujisaki, Keita Xagawa
Advances in Cryptology - ASIACRYPT 2016 - 22nd International Conference on the Theory and Application of Cryptology and Information Security 908 - 938 2016
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Groth-Sahai Proofs Revisited Again: A Bug in "Optimized" Randomization.
Keita Xagawa
IACR Cryptology ePrint Archive 2016 476 - 476 2016
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Ryo Nishimaki, Keita Xagawa
Designs, Codes and Cryptography 77 ( 1 ) 61 - 98 2015
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Efficient RKA-Secure KEM and IBE Schemes Against Invertible Functions.
Eiichiro Fujisaki, Keita Xagawa
Progress in Cryptology - LATINCRYPT 2015 - 4th International Conference on Cryptology and Information Security in Latin America(LATINCRYPT) 3 - 20 2015
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Accumulable Optimistic Fair Exchange from Verifiably Encrypted Homomorphic Signatures.
Jae Hong Seo, Keita Emura, Keita Xagawa, Kazuki Yoneyama
Applied Cryptography and Network Security - 13th International Conference(ACNS) 192 - 214 2015
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Secure Hierarchical Identity-Based Identification without Random Oracles.
Atsushi Fujioka, Taiichi Saito, Keita Xagawa
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences 97-A ( 6 ) 1307 - 1317 2014
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Non-malleable Multiple Public-Key Encryption.
Atsushi Fujioka, Eiichiro Fujisaki, Keita Xagawa
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences 97-A ( 6 ) 1318 - 1334 2014
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Martin R. Albrecht, Jean-Charles Faugère, Robert Fitzpatrick, Ludovic Perret, Yosuke Todo, Keita Xagawa
Public-Key Cryptography - PKC 2014 - 17th International Conference on Practice and Theory in Public-Key Cryptography 446 - 464 2014
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Ryo Nishimaki, Keita Xagawa
Public-Key Cryptography - PKC 2013 - 16th International Conference on Practice and Theory in Public-Key Cryptography 405 - 422 2013
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Message Authentication Codes Secure against Additively Related-Key Attacks.
Keita Xagawa
IACR Cryptology ePrint Archive 2013 111 - 111 2013
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Strongly Secure Authenticated Key Exchange from Factoring, Codes, and Lattices.
Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, Kazuki Yoneyama
Public Key Cryptography - PKC 2012 - 15th International Conference on Practice and Theory in Public Key Cryptography 467 - 484 2012
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Security Enhancement of Identity-Based Identification with Reversibility.
Atsushi Fujioka, Taiichi Saito, Keita Xagawa
Information and Communications Security - 14th International Conference(ICICS) 202 - 213 2012
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Secure Hierarchical Identity-Based Identification without Random Oracles.
Atsushi Fujioka, Taiichi Saito, Keita Xagawa
Information Security - 15th International Conference(ISC) 258 - 273 2012
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Security Enhancements by OR-Proof in Identity-Based Identification. Reviewed
Atsushi Fujioka, Taiichi Saito, Keita Xagawa
Applied Cryptography and Network Security - 10th International Conference(ACNS) 135 - 152 2012
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Applicability of OR-Proof Techniques to Hierarchical Identity-Based Identification.
Atsushi Fujioka, Taiichi Saito, Keita Xagawa
Cryptology and Network Security(CANS) 169 - 184 2012
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Security of Encryption Schemes in Weakened Random Oracle Models. Reviewed
Akinori Kawachi, Akira Numayama, Keisuke Tanaka, Keita Xagawa
Public Key Cryptography - PKC 2010, 13th International Conference on Practice and Theory in Public Key Cryptography 403 - 419 2010
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Zero-Knowledge Protocols for NTRU: Application to Identification and Proof of Plaintext Knowledge. Reviewed
Keita Xagawa, Keisuke Tanaka
Provable Security(ProvSec) 198 - 213 2009
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Multi-bit Cryptosystems Based on Lattice Problems. Reviewed
Akinori Kawachi, Keisuke Tanaka, Keita Xagawa
Public Key Cryptography - PKC 2007, 10th International Conference on Practice and Theory in Public-Key Cryptography 315 - 329 2007
Research Projects
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格子に基づく最悪時/平均時の関係を持つ電子署名および認証方式の構成
Grant number：07J55201 2007 - 2009
日本学術振興会 科学研究費助成事業 特別研究員奨励費 特別研究員奨励費
草川 恵太
Grant amount：\1200000 （ Direct Cost: \1200000 ）
研究計画に基づき格子を利用した認証方式および署名方式を構成した。また、これまでに得られた知見を元に、認証方式の構成、既存の暗号方式の改良、新しい暗号方式の提案を行った。これらは、量子計算機であっても困難であると考えられている問題に基づいており、高い安全性を期待できる方式である。
各研究の具体的内容は以下である。
1.昨年度構成した格子問題に基づく認証用プロトコルの応用を行った。NTRUと呼ばれる多項式を用いた暗号方式がある。これと、先の認証用プロトコルの類似点を用いて、NTRUに適したゼロ知識証明プロトコルを提案した。また、NTRU暗号の困難性に安全性の根拠をおく認証方式を提案した。今までNTRUに基づいた認証方式は無かった。
2.昨年度に引き続き、イデアル格子に基づく暗号方式の研究を行った。電子署名、認証方式に引き続き、公開鍵暗号方式、IDベース暗号方式を構成し、その安全性を証明した。これにより既存の格子暗号の鍵サイズや計算効率を上げることができる。
3.代理人再暗号化と呼ばれる暗号方式がある。代理人は変換鍵を所持している場合、暗号文の中身を知ることなく、ある受信者用の暗号文を別の受信者用の暗号文に変換できる。2005年に提案されたRegev暗号に着目し、新たなアルゴリズムを加えることで、代理人再暗号化方式を構成した。既存の代理人再暗号化方式は全て離散対数問題と呼ばれる数論的な問題に基づいている。よって、今回,初めて組合わせ系の問題に基づいて代理人再暗号化方式を構成したことになる。