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 by Year

Journals, Conferences, and Preprints

  1. [AC:XIUTH21] Fault-Injection Attacks against NIST's Post-Quantum Cryptography Round 3 KEM Candidates
    Keita Xagawa, Akira Ito, Rei Ueno, Junko Takahashi, and Naofumi Homma
    ASIACRYPT 2021 Part XX, LNCS XXXXX, pp.XX-XX (2020/XX)
    See also ia.cr/2021/840 [EPRINT:XIUTH21]
  2. [SAC:Xagawa21] The Boneh-Katz Transformation, Revisited: Pseudorandom/Obliviously-Samplable PKE from Lattices and Codes and Its Application
    Keita Xagawa
    SAC 2021, LNCS XXXXX, pp.XX-XX (2020/XX)
    See also ia.cr/2021/740 [EPRINT:Xagawa21a]
  3. [EPRINT:UXTITH21] Curse of Re-encryption: A Generic Power/EM Analysis on Post-Quantum KEMs
    Rei Ueno, Keita Xagawa, Yutaro Tanaka, Akira Ito, Junko Takahashi, and Naofumi Homma
    ia.cr/2021/849 (2021/06)
  4. [EPRINT:Xagawa21b] NTRU leads to Anonymous, Robust Public-Key Encryption
    Keita Xagawa
    ia.cr/2021/741 (2021/06)
  5. [EPRINT:ABNXXY21] Cryptanalysis of Boyen’s Attribute-Based Encryption Scheme in TCC 2013
    Shweta Agrawal, Rajarshi Biswas, Ryo Nishimaki, Keita Xagawa, Xiang Xie, and Shota Yamada
    ia.cr/2021/505 (2021/04)
  6. [AC:YKXT20] Non-Committing Encryption with Constant Ciphertext Expansion from Standard Assumptions
    Yusuke Yoshida, Fuyuki Kitagawa, Keita Xagawa, and Keisuke Tanaka
    ASIACRYPT 2020 Part II, LNCS 12492, pp.36-65 (2020/12)
    See also ia.cr/2020/1210
  7. [TCS:HSTX20] Quantum algorithm for the multicollision problem
    Akinori Hosoyamada, Yu Sasaki, Seiichiro Tani, and Keita Xagawa
    Theoretical Computer Science, 842, pp.100-117 (2020/11)
    See also ia.cr/2018/1122 and arXiv:1811.08097
  8. [ASIACCS:CPSWX20] ModFalcon: Compact Signatures Based On Module-NTRU Lattices
    Chitchanok Chuengsatiansup, Thomas Prest, Damien Stehlé, Alexandre Wallet, and Keita Xagawa
    ACM AsiaCCS 2020, pp.853-866 (2020/10)
    See also ia.cr/2019/1456
  9. [RSA:FerXag20] Post-Quantum Provably-Secure Authentication and MAC from Mersenne Primes
    Houda Ferradi and Keita Xagawa
    CT-RSA 2020, LNCS 12006, pp.469-495 (2020/02)
    See also ia.cr/2019/409
  10. [DCC:ABDGLTX20] 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, and Keita Xagawa
    Designs, Codes and Cryptography, 88(4), pp.643-653 (2020/04); First online: 16 December 2019
    Available in Springer's WebSite. The results of Song, Huang, Mu, and Wu got accepted on Dec. 21st 2018 at PKC'19, made available as ePrint 2019/053 on Jan. 25th 2019, a cryptanalysis implementation was publicly released on Jan. 30th 2019 by Deneuville et al. (github:deneuville/cryptanalysisSHMW), Lau and Tan (arXiv:1902.00241v1), then Xagawa (ia.cr/2019/120) published independently a description of the attack. The paper has been withdrawn since, both from ePrint and PKC'19, around Feb. 26th 2019. This work merges the implementation of Aragon et al., and the works of Lau and Tan, and Xagawa.
  11. [AC:HhaXagYam19] Quantum Random Oracle Model with Auxiliary Input
    Minki Hhan, Keita Xagawa, and Takashi Yamakawa
    Asiacrypt 2019 Part I, LNCS 11921, pp.584-614 (2019/12)
    See also ia.cr/2019/1093
  12. [PQCRYPTO:HSTX19] Improved Quantum Multicollision-Finding Algorithm
    Akinori Hosoyamada, Yu Sasaki, Seiichiro Tani, and Keita Xagawa
    PQCrypto 2019, LNCS 11505, pp.350-367 (2019/05)
    See [TCS:HSTX20]. See also ia.cr/2018/1122 and arXiv:1811.08097
  13. [PQCRYPTO:XagYam19] (Tightly) QCCA-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model
    Keita Xagawa and Takashi Yamakawa
    PQCrypto 2019, LNCS 11505, pp.249-268 (2019/05)
    See also ia.cr/2018/838
  14. [EC:SaiXagYam18] Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model
    Tsunekazu Saito, Keita Xagawa, and Takashi Yamakawa
    EUROCRYPT 2018 Part III, LNCS 10822, pp.520-551 (2018/04)
    See also ia.cr/2017/1005
  15. [RSA:BooTibXag18] Cryptanalysis of Compact-LWE
    Jonathan Bootle, Mehdi Tibouchi and Keita Xagawa
    CT-RSA 2018, LNCS 10808, pp.80-97 (2018/04)
    See also ia.cr/2017/742
  16. [PQCRYPTO:Xagawa18] Practical Cryptanalysis of a Public-key Encryption Scheme Based on Non-linear Indeterminate Equations at SAC 2017
    Keita Xagawa
    PQCrypto 2018, LNCS 10786, pp.142-161 (2018/04)
    See also ia.cr/2017/1224
    Note: I have reported the attacks in this paper to the original authros, Akiyama et al. Their submission "Giophantus" in NIST PQC Round~1 and their revised paper ia.cr/2017/1241 reflect the attacks in this paper.
  17. [IJIS:SEXY18] Accumulable Optimistic Fair Exchange from Verifiably Encrypted Homomorphic Signatures
    Jae Hong Seo, Keita Emura, Keita Xagawa, and Kazuki Yoneyama
    International Journal of Information Security, 17(2), pp.193-220 (2018/04); First Online: 22 March 2017
    Available at https://dx.doi.org/10.1007/s10207-017-0367-z.
  18. [EPRINT:Xagawa18] Practical Attack on RaCoSS-R
    Keita Xagawa
    ia.cr/2018/831
  19. [AC:HosSasXag17] Quantum Multicollision-Finding Algorithm
    Akinori Hosoyamada, Yu Sasaki, and Keita Xagawa
    ASIACRYPT 2017 Part II, LNCS 10625, pp.179-210 (2017/12)
    See also [TCS:HSTX20]. See also ia.cr/2017/864
  20. [SIGMOD:HorKikXag17] Cryptanalysis of Comparable Encryption in SIGMOD'16
    Caleb Horst, Ryo Kikuchi, and Keita Xagawa
    SIGMOD 2017, pp.1069-1084 (2017/05)
    Summary: We cryptanalyze cryptosystems proposed by Karras et al. (SIGMOD'16).
  21. [AC:FujXag16] Public-Key Cryptosystems Resilient to Continuous Tampering and Leakage of Arbitrary Functions
    Eiichiro Fujisaki and Keita Xagawa
    ASIACRYPT 2016 Part I, LNCS 10031, pp.908-938 (2016/12)
  22. [EPRINT:Xagawa16] Groth-Sahai Proofs Revisited Again: A Bug in ``Optimized'' Randomization
    Keita Xagawa
    ia.cr/2016/476
  23. [DCC:NisXag15] Verifiably encrypted signatures with short keys based on the decisional linear problem and obfuscation for encrypted VES
    Ryo Nishimaki and Keita Xagawa
    Designs, Codes, and Crypography, 77(1), pp.61-98 (2015/10); First online: 24 June 2014
  24. [DCC:FSXY15] Strongly secure authenticated key exchange from factoring, codes, and lattices
    Atsushi Fujioka, Koutarou Suzuki, Keita Xagawa, and Kazuki Yoneyama
    Designs, Codes and Cryptography, 76(3), pp.469-504 (2015/09); First online: 23 April 2014
    The journal version of [PKC:FSXY12]. See also ia.cr/2012/211
  25. [LATINCRYPT:FujXag15] Efficient RKA-Secure KEM and IBE Schemes Against Invertible Functions
    Eiichiro Fujisaki and Keita Xagawa
    LATINCRYPT 2015, LNCS 9230, pp.3-20 (2015/08)
  26. [ACNS:SEXY15] Accumulable Optimistic Fair Exchange from Verifiably Encrypted Homomorphic Signatures
    Jae Hong Seo, Keita Emura, Keita Xagawa, and Kazuki Yoneyama
    ACNS 2015, LNCS 9092, pp.192-214 (2015/06)
    See the journal version [IJIS:SEXY18]
  27. [IEICE:NisXag15] Key-Private Proxy Re-Encryption from Lattices, Revisited
    Ryo Nishimaki and Keita Xagawa
    IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E98-A, No.1, pp.100-116. (2015/01)
    An extended construction of [PKC:CCLNX14]
  28. [EPRINT:FujXag15] Note on the RKA security of Continuously Non-Malleable Key-Derivation Function from PKC 2015
    Eiichiro Fujisaki and Keita Xagawa
    ia.cr/2015/1088
  29. [IEICE:FujFujXag14] Non-malleable Multiple Public-Key Encryption
    Atsushi Fujioka, Eiichiro Fujisaki, and Keita Xagawa
    IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E97-A, No.6, pp.1318-1334. (2014/06)
  30. [IEICE:FujSaiXag14] Secure Hierarchical Identity-Based Identification without Random Oracles
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences, Vol.E97-A, No.6, pp.1307-1317. (2014/06)
  31. [PKC:AFFPTX14] 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 8383, pp.446-464 (2014/03)
    [EPRINT:AFFP13] + [EPRINT:TodXag13]
  32. [PKC:CCLNX14] 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 8383, pp.95-112 (2014/03)
    See also ia.cr/2015/491. See also [IEICE:NisXag15] for a key-private PRE from lattices.
  33. [ASIACCS:FSXY13] 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 (2013/05)
  34. [PKC:Xagawa13] Improved (Hierarchical) Inner-Product Encryption from Lattices
    Keita Xagawa
    PKC 2013, LNCS 7778, pp.235-252 (2013/02-03)
    See ia.cr/2015/249 for the full version.
  35. [PKC:NisXag13] 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 (2013/02-03)
    See [DCC:NisXag15] and ia.cr/2015/248 for the full version.
  36. [EPRINT:TodXag13] Cryptanalysis of the Huang-Liu-Yang Cryptosystem from PKC 2012
    Yosuke Todo and Keita Xagawa
    ia.cr/2013/481
    See [PKC:AFFPTX14] for the merged paper.
  37. [EPRINT:Xagawa13] Message Authentication Codes Secure against Additive Related-Key Attacks
    Keita Xagawa
    ia.cr/2013/111
  38. [CANS:FujSaiXag12] 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)
  39. [ICICS:FujSaiXag12] Security Enhancement of Identity-Based Identification with Reversibility
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    ICICS 2012, LNCS 7618, pp.202-213 (2012/10)
  40. [ISC:FujSaiXag12] Secure Hierarchical Identity-Based Identification without Random Oracles
    Atsushi Fujioka, Taiichi Saito, and Keita Xagawa
    ISC 2012, LNCS 7483, pp.258-273 (2012/09)
  41. [ACNS:FujSaiXag12] 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)
  42. [PKC:FSXY12] 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 [DCC:FSXY15] and ia.cr/2012/211 for the full version.
  43. [PKC:KNTX10] 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 ia.cr/2010/122 for the full version.
  44. [AC:SSTX09] 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 ia.cr/2009/285 for the draft of the full version.
  45. [PROVSEC:XagTan09] 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)
  46. [AC:KawTanXag08] 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]
  47. [AAAC:XagTan08] A Compact Signature Scheme with Ideal Lattice (Extended Abstract) (1-page)
    Keita Xagawa and Keisuke Tanaka
    AAAC 2008
    This work is superseded by [AC:SSTX09].
    [2008AAAC.pdf] [Slides:20080426_AAAC.pdf]
  48. [PKC:KawTanXag07] 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]

Domestic Symsioum/Conference/Workshop

  1. [SCIS:Xagawa21] Boneh-Katz変換再訪
    草川 恵太
    SCIS 2021 1A1-2 (2021/01)
  2. [SCIS:Xagawa20] 暗号方式構成の効率の限界について
    草川 恵太
    SCIS 2020 1A1-2 (2020/01)
  3. [SCIS:NTXM19] GLP署名の故障利用攻撃に対する安全性評価
    長濱 拓季, 藤堂 洋介, 草川 恵太, 森井 昌克
    SCIS 2019 2D4-1 (2019/01)
  4. [SCIS:Xagawa19] Practical Attack on RaCoSS-R
    RaCoSS-Rへの実時間攻撃
    Keita Xagawa
    SCIS 2019 3B2-5 (2019/01)
  5. [SCIS:Xagawa18] Practical Cryptanalysis of a Public-key Encryption Scheme Based on Non-linear Indeterminate Equations at SAC 2017: Extended Abstract
    「非線型不定方程式に基づく公開鍵暗号」への実時間攻撃
    Keita Xagawa
    SCIS 2018 1B2-3 (2018/01)
  6. [SCIS:KOSXKH18] KEMを用いた動的多者鍵配布プロトコル
    金城 皓羽, 岡野 裕樹, 齋藤 恆和, 草川 恵太, 小林 鉄太郎, 星野 文学
    SCIS 2018 3A2-1 (2018/01)
  7. [SCIS:NFTXM18] 整数計画法を用いた平文回復攻撃による二値行列LWE暗号の安全性評価
    長濱 拓季, 船引 悠生, 藤堂 洋介, 草川 恵太, 森井 昌克
    SCIS 2018 4A1-2 (2018/01)
  8. [SCIS:Xagawa17:3E4-3] Cryptanalysis of "Proxy Re-Encryption Schemes with Key Privacy from LWE"
    「LWEに基づく再暗号化鍵匿名性を持つ代理人再暗号化方式」に対する攻撃
    Keita Xagawa
    SCIS 2017 3E4-3 (2017/01).
    We show that a new version of the KP-PRE from LWE [ia.cr/2016/327] is neither CCA2-secure nor key-private in the CCA setting.
  9. [SCIS:Xagawa17:2E3-3] 自己破壊可能回路を許す公開鍵暗号の安全性の分離
    Keita Xagawa
    SCIS 2017 2E3-3 (2017/01).
    There exists a PKE which is NM-SDA-secure but not IND-CCA2-seucre.
  10. [SCIS:Xagawa16] Groth-Sahai Proofs Revisited Again: A Bug in ``Optimized'' Randomization
    Groth-Sahai証明再々訪
    Keita Xagawa
    SCIS 2016 3E3-1 (2016/01)
  11. [SCIS:FujXag15] 防御不可能なタンパリング以外のほぼ全てのタンパリングから暗号回路を守る方法
    Eiichiro Fujisaki and Keita Xagawa
    SCIS 2015 3D3-1 (2015/01)
  12. [SCIS:SEXY15:2E4-4] Verifiably Encrypted Homomorphic Signatures
    検証可能暗号化準同型署名
    Jae Hong Seo, Keita Emura, Keita Xagawa, and Kazuki Yoneyama
    SCIS 2015 2E4-4 (2015/01)
  13. [SCIS:SEXY15:1E1-5] Accumulable Optimistic Fair Exchange
    ツケ払いに適した楽観的公平交換
    Jae Hong Seo, Keita Emura, Keita Xagawa, and Kazuki Yoneyama
    SCIS 2015 1E1-5 (2015/01)
  14. [SCIS:HTXM14] 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)
  15. [SCIS:KanXagTak14] 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)
  16. [SCIS:CCLNX14] 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)
    See [PKC:CCLNX14]
  17. [SCIS:Xagawa14] RKA-KDM-CCA secure public-key encryption scheme
    Keita Xagawa
    SCIS 2014 4E2-2 (2014/01)
  18. [SCIS:Xagawa13] 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)
    See [EPRINT:Xagawa13]
  19. [SCIS:FujXag13] 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)
  20. [SCIS:Xagawa12] 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)
  21. [SCIS:YXSF11] 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)
    See [PKC:FSXY12]
  22. [SCIS:Xagawa11] 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)
  23. [SCIS:XagTan10] 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]
  24. [SCIS:XagKaw10] 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)
  25. [SCIS:XagTan09:4A2-5] 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)
    See [AC:SSTX09] (and my Ph.D Thesis)
    [Slides in Japanese:20090123_SCIS_IdealLWE.pdf]
  26. [SCIS:XagTan09:3F2-5] 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]
  27. [SCIS:XagTan09:3F2-4] 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)
    See [PROVSEC:XagTan09]
    [Slides in Japanese:20090122_SCIS_NTRU-ZK.pdf]
  28. [SCIS:NXKT09:3D1-2] 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)
    See [PKC:KNTX10]
  29. [SCIS:NXKT09:3D1-1] 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)
    See [PKC:KNTX10]
    [Slides in Japanese: 20080723_LA.pdf], [Slides in Japanese: 20090122_SCIS_Dist.pdf]
  30. [SCIS:XagTan08] 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)
    See [AC:SSTX09] (and my Ph.D Thesis)
    [Slides in Japanese: 20080124_SCIS_Ideal.pdf]
  31. [SCIS:XagKawTan08] 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), LA Symposium 2007 Summer 11 (2007/07)
    See [AC:KawTanXag08] and my Ph.D Thesis
    [TR: C-249.pdf], [Slides in Japanese: 20080124_SCIS_SID.pdf]
  32. [SCIS:XagKawTan07:1C1-2] 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]
  33. [SCIS:XagKawTan07:1C1-1] 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]
  34. [SCIS:XagKawTan06] 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)
    See [PKC:KawTanXag07] and my master thesis
    [Slides in Japanese: 20060128_LA.pdf]

Thesis

Lectures

  1. 2021-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda, Ryo Nishimaki, and Keisuke Tanaka.
    XXXXxNの予定
  2. 2020-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda and Ryo Nishimaki.
    攻撃×4の予定
    See slides and problems in gitlab.com/xagawa/titech20
  3. 2019-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda and Ryo Nishimaki.
    秘密分散と秘密計算の予定
    See slides and problems in gitlab.com/xagawa/titech19
  4. 2018-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda and Ryo Nishimaki.
  5. 2017-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda and Ryo Nishimaki.
  6. 2016-Fall, XCO.T474: Theory of Cryptography for Cybersecurity
    XCO.T474: サイバーセキュリティ暗号理論
    At Tokyo Institute of Technology with Takahiro Matsuda and Ryo Nishimaki.
  7. 2014-Spring-75024: Topics on Mathematical and Computing Science VI
    2014-Spring-75024: 数理・計算科学特論第六
    At Tokyo Institute of Technology with Eiichiro Fujisaki and Ryo Nishimaki.
  8. 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. 耐量子計算機暗号の解説 ~符号暗号を中心として~
    Keita Xagawa
    SITA 2021 (2021/12)
  2. 量子攻撃・量子構成の下界について
    Keita Xagawa
    IEICE General Conference 2021 ADI-1. 信学会総合大会2021 ADI-1. 量子計算と暗号の進展 (2021/03)
  3. 量子攻撃・量子構成の下界について
    Keita Xagawa
    IEICE General Conference 2020 ADI-1. 信学会総合大会2020 ADI-1. 量子計算と暗号の発展 (2020/03)
    Due to COVID-19, the conference is missing...
  4. 耐量子暗号
    Keita Xagawa
    The 2nd YITP Quantum Information School 第二回基研量子情報スクール (2020/02)
    My slides in Japanese: http://www2.yukawa.kyoto-u.ac.jp/~tomoyuki.morimae/Xagawa.pdf
  5. 格子暗号の現状とこれから
    Keita Xagawa
    第51回 ISSスクエア水平ワークショップ 『Post-Quantum Cryptographyの現状とこれから』 (2018/01)
  6. Post-Quantum Cryptography in NTT
    Keita Xagawa
    3rd Asia Post-Quantum Cryptography Forum (2017/03)
  7. A brief summary of FHE, MLM, and iO with lattices (in 30 min.)
    AI-1-7. 完全準同型暗号, 多線形写像, 識別不能難読化の数学的基礎:特に格子問題
    Keita Xagawa
    IEICE General Conference AI-1. 信学会総合大会2015 AI-1. 最新暗号ツールの研究動向:完全準同型暗号、多線形写像、難読化 (2015/03)
  8. 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)
  9. Improved (Hierarchical) Inner-Product Encryption from Lattices
    Keita Xagawa
    PKC2013を勉強する会 (2013/06)
  10. A Survey on LWE-based Encryption Schemes
    Keita Xagawa
    Lattice Crypto Day 2012 Japan (LCD2012J) (2012/03)
  11. Brief History of Lattice Crypto World
    Keita Xagawa
    Lattice Crypto Day 2012 Japan (LCD2012J) (2012/03)
  12. 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]
  13. 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]
  14. A Survey on Lattice-Based Hash Functions
    Keita Xagawa
    New Horizons in Computing - Mini Meeting (Cryptography) (2007/03)
    [Slides in Japanese: 20070303_NHC.pdf]