Keita Xagawa (草川 恵太)

About

See Bibliography on Lattice-based Cryptosystems and Bibliography on Code-based Cryptosystems.

See DBLP: Keita Xagawa, Google Scholar: Keita Xagawa, and MAS: Keita Xagawa

Publications

Refereed International Conference Papers

  1. Practical Cryptanalysis of a Public-Key Encryption Scheme Based on New Multivariate Quadratic Assumptions
    Martin R. Albrecht, Jean-Charles Faugère, Robert Fitzpatrick, Ludovic Perret, Yosuke Todo, and Keita Xagawa
    PKC 2014, LNCS nnnn, pp.nnn-nnn (2014/03)
    See Cryptology ePrint Archive: 2009/285
  2. Re-encryption, functional re-encryption, and multi-hop re-encryption: A framework for achieving obfuscation-based security and instantiations from Lattices
    Nishanth Chandran, Melissa Chase, Feng-Hao Liu, Ryo Nishimaki, and Keita Xagawa
    PKC 2014, LNCS nnnn, pp.nnn-nnn (2014/03)
  3. Practical and Post-Quantum Authenticated Key Exchange from One-Way Secure Key Encapsulation Mechanism
    Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, and Kazuki Yoneyama
    ASIACCS 2013, pp.83-94 (2013/5)
  4. Improved (Hierarchical) Inner-Product Encryption from Lattices
    Keita Xagawa
    PKC 2013, LNCS 7778, pp.235-252 (2013/2-3)
  5. Verifiably Encrypted Signatures with Short Keys based on the Decisional Linear Problem and Obfuscation for Encrypted VES
    Ryo Nishimaki and Keita Xagawa
    PKC 2013, LNCS 7778, pp.405-422 (2013/2-3)
  6. Applicability of OR-Proof Techniques to Hierarchical Identity-Based Identification
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    CANS 2012, LNCS 7712, pp.169-184 (2012/12)
  7. Security Enhancement of Identity-Based Identification with Reversibility
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    ICICS 2012, LNCS 7618, pp.202-213 (2012/10)
  8. Secure Hierarchical Identity-Based Identification without Random Oracles
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    ISC 2012, LNCS 7483, pp.258-273 (2012/09)
  9. Security Enhancements by OR-Proof in Identity-Based Identification
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    ACNS 2012, LNCS 7341, pp.135-152 (2012/06)
  10. Strongly Secure Authenticated Key Exchange from Factoring, Codes, and Lattices
    Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, and Kazuki Yoneyama
    PKC 2012, LNCS 7293, pp.467-484 (2012/05)
    See also Cryptology ePrint Archive: 2012/211
  11. Security of Encryption Schemes in Weakened Random Oracle Models (Extended Abstract)
    Akinori Kawachi, Akira Numayama, Keisuke Tanaka, and Keita Xagawa
    PKC 2010, LNCS 6056, pp.403-419 (2010/05)
    See Cryptology ePrint Archive: 2010/122 for the full version.
  12. Efficient Public Key Encryption Based on Ideal Lattices (Extended Abstract)
    Damien Stehlé, Ron Steinfeld, Keisuke Tanaka, and Keita Xagawa
    ASIACRYPT 2009, LNCS 5912, pp.617-635 (2009/12)
    See Cryptology ePrint Archive: 2009/285 for the draft of the full version.
  13. Zero-Knowledge Protocols for NTRU: Application to Identification and Proof of Plaintext Knowledge
    Keita Xagawa and Keisuke Tanaka
    ProvSec 2009, LNCS 5848, pp.198-213 (2009/11)
    We propose zero-knowledge and proof-of-knowledge protocols for NTRU. One is for the relation on secret-key knowledge and the other for that on plaintext knowledge. They are the first non-trivial constructions of these protocols for NTRU. Additionally, the former directly yields an identification scheme based on NTRU. See also my Ph.D Thesis.
    [Draft: 2009TX-NTRUZK.pdf]
  14. Concurrently Secure Identification Schemes Based on the Worst-Case Hardness of Lattice Problems
    Akinori Kawachi, Keisuke Tanaka, and Keita Xagawa
    ASIACRYPT 2008, LNCS 5350, pp.372-389 (2008/12)
    Errata: in the introduction, I wrote that we can apply the ORing technique to the Lyubashevsky identification scheme. However, since there is no simulator in Lyubashevsky's proof, we cannot take OR the statements of Lyubashevsky's relations. See also my Ph.D Thesis.
    [Draft: 2008KTX-SID.pdf] [Slides:20081210_ASIA_SID.pdf]
  15. A Compact Signature Scheme with Ideal Lattice (Extended Abstract) (1-page)
    Keita Xagawa and Keisuke Tanaka
    AAAC 2008
    This work is superseded by “Efficient Public Key Encryption Based on Ideal Lattices” with Stehlé, Steinfeld, and Tanaka in ASIACRYPT 2009.
    [2008AAAC.pdf] [Slides:20080426_AAAC.pdf]
  16. Multi-bit Cryptosystems Based on Lattice Problems
    Akinori Kawachi, Keisuke Tanaka, and Keita Xagawa
    PKC 2007, LNCS 4450, pp.315-329 (2007/04)
    See also my master thesis.
    [Draft: 2007KTX.pdf] [Slides:20070418_PKC_MultiBit.pdf]

Unrefereed International/Domestic Workshops/Symposiums/Preprints

  1. GPGPUを用いたGSW13完全準同型暗号の高速実装
    Ryo Hirano, Yosuke Todo, Keita Xagawa, and Masakatu Morii
    SCIS 2014 1D3-1 (2014/01)
  2. 多変数公開鍵暗号Simple Matrix方式の復号化における問題点
    Yuta Kanno, Keita Xagawa, and Tsuyoshi Takagi
    SCIS 2014 3E1-4 (2014/01)
  3. 格子問題に基づく再暗号化方式の難読化について
    Nishanth Chandran, Melissa Chase, Feng-Hao Liu, Ryo Nishimaki, and Keita Xagawa
    SCIS 2014 4E1-4 (2014/01)
    #CCLNX14-PRE
  4. RKA-KDM-CCA secure public-key encryption scheme
    Keita Xagawa
    SCIS 2014 4E2-2 (2014/01)
  5. Cryptanalysis of the Huang-Liu-Yang Cryptosystem from PKC 2012
    Huang-Liu-Yang暗号 (PKC 2012) への攻撃
    Yosuke Todo and Keita Xagawa
    Cryptology ePrint Archive: 2013/481
    This work is superseded by “Practical Cryptanalysis of a Public-Key Encryption Scheme Based on New Multivariate Quadratic Assumptions” with Albrecht, Faugère, Fitzpatrick, Perret, and Todo in PKC 2014.
  6. Message Authentication Codes Secure against Additive Related-Key Attacks
    加法的関連鍵攻撃に対して安全なメッセージ認証符号
    Keita Xagawa
    SCIS 2013 1B1-2 (2013/01), Cryptology ePrint Archive: 2013/111
  7. 可逆なタンパー関数に耐性を持つ暗号学的回路
    Eiichiro Fujisaki and Keita Xagawa
    SCIS 2013 2B2-3 (2013/01)
  8. An Attack on Key-Exchange Protocols Proposed by Accardi et al.
    Accardiらの鍵共有プロトコルに対する攻撃
    Keita Xagawa
    SCIS 2012 2A2-2 (2012/01-02)
  9. 格子問題、符号理論、および素因数分解問題に基づく強い認証鍵交換: KEMからの一般構成
    Kazuki Yoneyama, Keita Xagawa, Koutarou Suzuki, and Atsushi Fujioka
    SCIS 2011 3F4-1 (2011/01)
    This work is superseded by “Strongly Secure Authenticated Key Exchange from Factoring, Codes, and Lattices” with Fujioka, Suzuki, and Yoneyama in PKC 2012.
  10. Indistinguishability against Related-Key Attacks in the Public-Key Settigns and Bidrectional Proxy Re-Encryption
    関連鍵攻撃に対する識別不可能性と双方向代理人再暗号化
    Keita Xagawa
    SCIS 2011 2A2-5 (2011/01)
  11. Proxy Re-Encryption based on Learning with Error
    格子に基づく代理人再暗号化
    Keita Xagawa and Keisuke Tanaka
    ASIACRYPT 2009 Rump Session (2009/12), SCIS 2010 2A3-3 (2010/01), LA Symposium 2009 Winter 7 (2010/02)
    See also my Ph.D Thesis.
    [Slides:20100120_SCIS_PRE.pdf]
  12. Pseudorandomness of the Legendre Sequences and Robust Quantum State Decoding (old title:Simultaneous Security of Quantum Hardcore Functions)
    ルジャンドル列の擬似乱数性と頑健な量子状態復号 (旧タイトル:量子ハードコア関数の同時安全性)
    Keita Xagawa and Akinori Kawachi
    LA Symposium 2009 Summer 4 (2009/07), SCIS 2010 4B1-1 (2010/01)
  13. An IND-CCA2 Secure Encryption Scheme from an Ideal LWE Assumption
    イデアル版LWE仮定に基づくIND-CCA2安全な暗号方式
    Keita Xagawa and Keisuke Tanaka
    SCIS 2009 4A2-5 (2009/01)
    This work is superseded by “Efficient Public Key Encryption Based on Ideal Lattices” with Stehlé, Steinfeld, and Tanaka in ASIACRYPT 2009. See also my Ph.D Thesis.
    [Slides in Japanese:20090123_SCIS_IdealLWE.pdf]
  14. NFALSE: Another Ring-Based Public Key Cryptosystem with Faster Encryption
    NFALSE: 多項式環に基づくより高速な公開鍵暗号
    Keita Xagawa and Keisuke Tanaka
    SCIS 2009 3F2-5 (2009/01), LA Symposium 2008 Winter 26 (2009/02)
    [Slides in Japanese:20090122_SCIS_NFALSE.pdf]
  15. Zero-Knowledge Protocols for NTRU
    NTRU暗号に対するゼロ知識証明
    Keita Xagawa and Keisuke Tanaka
    SCIS 2009 3F2-4 (2009/01)
    This work is superseded by “Zero-Knowledge Protocols for NTRU: Application to Identification and Proof of Plaintext Knowledge” with Tanaka in ProvSec 2009. See also my Ph.D Thesis.
    [Slides in Japanese:20090122_SCIS_NTRU-ZK.pdf]
  16. RSA-OAEP is secure in the Weakened Random Oracle Models
    Akira Numayama, Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2009 3D1-2 (2009/01)
    This work is superseded by “Security of Encryption Schemes in Weakened Random Oracle Models (Extended Abstract)” with Kawachi, Numayama, and Tanaka in PKC 2010.
  17. Sampling Methods Revisited: Approximation Sampling with Huge Parameters
    近似サンプリング法の精度保証
    Akira Numayama, Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2009 3D1-1 (2009/01), LA Symposium 2008 Summer 15 (2008/07)
    This work is superseded by “Security of Encryption Schemes in Weakened Random Oracle Models (Extended Abstract)” with Kawachi, Numayama, and Tanaka in PKC 2010.
    [Slides in Japanese: 20080723_LA.pdf], [Slides in Japanese: 20090122_SCIS_Dist.pdf]
  18. A Compact Signature Scheme with Ideal Lattice (Extended Abstract)
    イデアル格子問題に基づくコンパクトな署名方式
    Keita Xagawa and Keisuke Tanaka
    SCIS 2008 3D3-2 (2008/01)
    This work is superseded by “Efficient Public Key Encryption Based on Ideal Lattices” with Stehlé, Steinfeld, and Tanaka in ASIACRYPT 2009. See also my Ph.D Thesis.
    [Slides in Japanese: 20080124_SCIS_Ideal.pdf]
  19. Concurrently Secure Identification Schemes and Ad Hoc Anonymous Identification Schemes Based on the Worst-Case Hardness of Lattice Problems
    格子問題に基づく高い安全性をもつ認証方式
    Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2008 3D3-1 (2008/01), Technical Report (2007/11)
    This work is superseded by “Concurrently Secure Identification Schemes Based on the Worst-Case Hardness of Lattice Problems” in ASIACRYPT 2008. An old version appeared in LA Symposium 2007 Summer 11 (2007/07). See also my Ph.D Thesis.
    [TR: C-249.pdf], [Slides in Japanese: 20080124_SCIS_SID.pdf]
  20. Proof of Plaintext Knowledge for the Regev Cryptosystems
    Regev暗号に対する平文知識証明
    Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2007 1C1-2 (2007/01), Technical Report (2007/01)
    See also my master's thesis.
    [TR: C-236.pdf] [Slides in Japanese: 20070123_SCIS_PPK.pdf]
  21. A Lattice-Based Cryptosystem and Proof of Knowledge on Its Secret Key
    格子暗号の秘密鍵についての知識証明
    Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2007 1C1-1 (2007/01), LA Symposium Winter 2006 7 (2007/02), Technical Report (2007/01)
    SCIS 2007 Award, LA/EATCS Best Presentation Award. See also my master's thesis.
    [TR: C-235.pdf] [Slides in Japanese: 20070123_SCIS_PSK.pdf]
  22. Multi-bit Cryptosystems Based on Lattice Problems
    格子問題に基づく複数ビット公開鍵暗号方式
    Keita Xagawa, Akinori Kawachi, and Keisuke Tanaka
    SCIS 2006 2A4-4 (2006/01), LA Winter 2005 7 (2006/01)
    This work is superseded by “Multi-bit Cryptosystems Based on Lattice Problems” in PKC 2007. See also my master's thesis.
    [Slides in Japanese: 20060128_LA.pdf]

Thesis

Lectures

  1. 2013-Spring-75024: Topics on Mathematical and Computing Science VI
    2013-Spring-75024: 数理・計算科学特論第六
    At Tokyo Institute of Technology with Ryo Nishimaki.

Talks

  1. Practical Cryptanalysis of a Public-Key Encryption Scheme Based on New Multivariate Quadratic Assumptions
    Keita Xagawa
    Workshop: Post-Quantum Cryptography and Its Related Topics (2013/12)
  2. Improved (Hierarchical) Inner-Product Encryption from Lattices
    Keita Xagawa
    PKC2013を勉強する会 (2013/06)
  3. A Survey on LWE-based Encryption Schemes
    Keita Xagawa
    Lattice Crypto Day 2012 Japan (LCD2012J) (2012/03)
  4. Brief History of Lattice Crypto World
    Keita Xagawa
    Lattice Crypto Day 2012 Japan (LCD2012J) (2012/03)
  5. Lattice-based Hash Functions
    格子に基づく安全なハッシュ関数の構成
    Keita Xagawa
    Workshop on interaction between CRyptography, Information Security and MATHematics (CRISMATH) 暗号及び情報セキュリティと数学の相関ワークショップ (2010/02)
    [Slides in Japanese: 20100224.pdf]
  6. Efficient Public Key Encryption Based on Ideal Lattices
    イデアル格子で作る公開鍵暗号方式、他
    Keita Xagawa
    4th Secure Construction of PKC and Its Applications Workshop 第4回公開鍵暗号の安全な構成とその応用ワークショップ (2010/02)
    [Slides in Japanese: 20100223_Workshop.pdf]
  7. A Survey on Lattice-Based Hash Functions
    Keita Xagawa
    New Horizons in Computing - Mini Meeting (Cryptography) (2007/03)
    [Slides in Japanese: 20070303_NHC.pdf]