Main Publications

• Yasuyuki SAKAI and Kouichi SAKURAI , "On the Practical Performance of Hyperelliptic Curve Cryptosystems in Software Implementation," IEICE Trans. Vol.E83-A No.4, pp.692-703 (2000 Apri.)
• Kouichi SAKURAI , "A Progress Report on Lattice Based Public-Key Cryptosystems -- Theoretical Security versus Practical Cryptanalysis --," (Invited survey) IEICE Trans. IEICE Trans. Vol.E83-D No.3, pp.570-579 (2000 Mar).
• T.Itoh, M.Burmester, Y.Desmdet, K.SAKURAI, and H.Shizuya, "Divertible and subliminal-free zero-knowledge proofs for languages," J. of Cryptology Vol.12, pp.197-223 (1999)
• Shingo MIYAZAKI and Kouichi SAKURAI , "A practical off-line digital-money system with partilly blind signatures based on the discrete logarithm problem,'' IEICE Transactions, EA: Special section on Cryptography and Information Security (2000, Jan.).
• E. Dannoura and K.Sakurai, ``An improvement of ElYaniv-Fiat-Karp-Tarpin's money-making bi-directional strategy,'' Information Processing Letters, Vol.66, No.1, 15 April 1998, pp.27-33.
• K.Sakurai and H. Shizuya, ``A Structural comparison of the computational difficulty of breaking discrete log cryptosystems.'' J. of Cryptology Vol.11, No.1, pp. 29-43 (1998).
• K.Sakurai, ``Practical proofs of knowledge without relying on theoretical proofs of membership of languages,'' Theoretical Computer Science, Vol.181, No.2, pp.317-335 (30 July 1997), an invited paper in the special issue of 1st International Computing and Combinatorics Conference (1997).
• Kouichi Sakurai and Y. Zheng, ``Non-randomness from a block cipher with provable immunity against linear cryptanalysis,'' IEICE Transactions:special section on cryptography and information security, Vol.E80-A, No.1,pp.19-24 (Jan.1997)
• E. Dannoura, and K.Sakurai, ``An improved on-line algorithm for money trading and its performance,'' (Written in Japanese) Journal of Information Processing Society of Japan, Vol.32, No.12, pp.2161-2169 (Dec.1996).
• Y. Akio, andK.Sakurai, ``A short certificate of the number of universal optimal strategies for stopping simple stochastic games,'' Information Processing Letters, 57, pp.17-24 (1996).
• T.Okamoto, K.Sakurai, and H.Shizuya, ``On the complexity of the discrete logarithm for a general finite group'', IEICE Transactions:special section on cryptography and information security, Vol.E79-A, No.1 (Jan.1996)
• K.Sakurai, T.Itoh, ``Subliminal channels transferring signatures -- Yet another cryptographic primitive.'' IEICE Transactions:special section on cryptography and information security, Vol.E77-A, No.1 (1994)
• T.Itoh and K.Sakurai, ``Constant round perfect ZKIP of computational ability,'' IEICE Transactions, Vol.E76-A, No.7 (1993)
• K.Sakurai, ``A characterization of languages in constant round perfect zero-knowledge interactive proofs,'' IEICE Transactions, Vol.E76-A, special section on Discrete Math. and its applications (1993)
• T.Itoh and K.Sakurai, ``On the complexity of constant round ZKIP of possession of knowledge,'' IEICE Transactions, Vol.E76-A, No.1 (1993)
• K.Sakurai and T.Itoh, ``Practical consequences of the discrepancy between zero-knowledge protocols and their parallel execution,'' IEICE Transactions, Vol.E76-A, No.1 (1993)
• H.Shizuya, T.Itoh, and K.Sakurai, ``On the complexity of hyperelliptic discrete logarithm problem,'' IEICE Transactions, Vol. E 74, No.8 (1991)
• K.Sakurai and T. Itoh, ``Language membership versus possession of knowledge in constant round ZKIP,'' IEICE Transactions, Vol. E 74, No.8 (1991)
• K.Sakurai and M. Yoshida, ``Fuchsian systems associated with the $P^{2}(F_2)$-arrangement,'' SIAM J. MATH. ANAL, Vol. 20, No.6 (1989)
• K.Sakurai and M. Suzuki, ``Equivalence problem and automorphisms of some Abelian branched coverings of the Riemann sphere,'' Memories of the Faculty of Science, Kyushu Univ. Ser.A, Math., Vol. XLII, No.2, pp.145-152 (1988)

NOTE: LNCS = Lecture Notes in Computer Science, Springer

• G. Di Crecenzo,K.Sakurai and M. Yung, "On zero-knowledge proofs: from membership to decision" Proc. ACM STOC2000. (To appear in May 2000}
• I. Duursma, and K.Sakurai, ``Efficient algorithms for the Jacobian variety of hyperelliptic curves $y^2 = x^p -x + 1$ over a finite field of odd characteristic $p$'' Coding Theory, Cryptography and related areas, Buchmann et al. edit.(1999) Springer.
• Yasuyuki Sakai and Kouichi Sakurai, ``Over $F_p$ vs. $F_{2^n}$ over and on Pentium vs. on Alpha in Software Implementation of Hyperelliptic Curve'' PreProc. 1999 International Conference on Information Security and Cryptology December 9-10, 1999 Korea University, Seoul, Korea, (PostProc. to appear from Springer LNCS.)
• Shingo MIYAZAKI, Kouichi Sakurai, and Moti YUNG, ``On Threshold RSA-Signing with no Dealer'' PreProc. 1999 International Conference on Information Security and Cryptology December 9-10, 1999 Korea University, Seoul, Korea, (PostProc. to appear from Springer LNCS.)
• Tetsuya Tamura and Kouichi Sakurai, ``A Hardware-Oriented Algorithm for Computing in Jacobians and Its Implementation for Hyperelliptic Cryptosystems'' PreProc. 1999 International Conference on Information Security and Cryptology December 9-10, 1999 Korea University, Seoul, Korea, (PostProc. to appear from Springer LNCS.)
• S.Miyazaki, and Kouichi Sakurai, "A Parallel Withstanding Attack with Forging Key Certificates on an Electronic Cash System Based on Message-Recovery Blind Digital Signatures'' Proc. International Workshop on Cryptographic Techniques \& E-Commerce, City University of Hong Kong Press, pp.163-169 (1999).
• Kouichi Sakurai and S.Miyazaki} ``A Bulletin-Board Based Digital Auction Scheme with Bidding Down Strategy - Towards Anonymous Electronic Bidding without Anonymous Channels nor Trusted Centers,'' Proc. International Workshop on Cryptographic Techniques \& E-Commerce, City University of Hong Kong Press, pp.180-187 (1999)
• S.Miyazaki, and Kouichi Sakurai, "Classification of Chaum-Fiat-Naor Paradigm based anonymous electronic cash systems accroding to vulunerability aganist insider-attacks from untrusted authorities" Proc. International Workshop on Cryptographic Techniques \& E-Commerce, City University of Hong Kong Press. pp.262-271 (1999).
• S.Miyazaki, I.Kuroda, and K. Sakurai, "Toward Fair International Key Escrow -- An attempt by distributed Trusted Third Agencies with threshold cryptography --" 1999 International Workshop on Practice and Theory in Public Key Cryptography, Springer LNCS (March 1999).
• Y.Sakai and K. Sakurai, "Design of Hyperelliptic Cryptosystems in Small Characteristic and a Software Implementation over $F_{2^n}$" Proc. of ASIACRYPT'98, LNCS Vol.1514 (Dec.1998)
• G. Di Crecenzo, K. Sakurai and M. Yung "Checking programs discreteetly: Demonstrating result-correctness efficiently while concealing it" Kyung-Yong Chwa and Oscar H. Ibarra (Eds.) Algorithms and Computation 9th International Symposium, ISAAC'98 Taejon, Korea, Dec. 1998, Proc. Lecture Notes in Computer Science Vol.1533, pp. 59-68 (1998).
• S.Miyazaki, and K. Sakurai ``An efficient untraceable electronic money system based on partially blind signatures of the discrete logarithm problem, '' PreProc. Financial Cryptology'98 (Proc. To appear in LNCS)
• M.David and K. Sakurai ``Security Issues for Contactless Smart Cards,'' PreProc. PKC'98: The Proc. is in LNCS 1431, pp. 247-352 (1998).
• Y.Sakai, K. Sakurai and M. Ishizuka, ``Secure hyperelliptic cryptosystems and their performance, '' PreProc. PKC'98: The Proc. is in LNCS 1431, pp.164-181 (1998).
• G. Di Crecenzo, K. Sakurai and M. Yung, ``Result-indistinguishable zero-knowledge proofs: increased power and constant-round protocols,'' Michael Morvan, Christoph Meinel, and Daniel Krob (Eds.) STACS 98, 15th Annual Symposium on Theoretical Aspects of Computer Science, Paris, France, February, 1998, Proceedings, Lecture Notes in Computer Science 1373, pp.511-521
• E.Dannoura and K. Sakurai, ``On-line versus off-line in money-making strategies with BROKERAGE,'' Proc. of 8th Annual International Symposium on Algorithms and Computation, LNCS 1350, pp.173-182 (1997).
• Y.Sakai, K. Sakurai and H. Ishizuka, ``On weak RSA-keys produced from Pretty Good Privacy,'' Proc. of 1st International Conference of Information and Communication Security (ICICS97) (Nov. 1997). LNCS 1334, pp.314-324.
• G. Di Crecenzo, K. Sakurai and M. Yung, ``Zero-knowledge proofs of decision power: new protocols and optimal rounnd-complexity,'' Proc. of 1st International Conference of Information and Communication Security (ICICS97) (Nov. 1997). LNCS 1334, pp.17-27.
• K. Sakurai, Y.Yamane, S.Shingo and T. Inoue, ``A key escrow systems with protecting users' privacy by blind decoding,'' PreProc. of 1997 Information Security Workshop (ISW97) (Sept. 1997). (The final version is in LNCS 1396, pp.147-157.)
• Y.Kaneko, F. Sano, and K. Sakurai , ``On provable security against differential and linear cryptanalysis in generalized Feistel ciphers with multiple random functions Proc. of SAC'97 (Aug. 1997).
• K. Sakurai and F. Souichi, ``Improving linear cryptanalysis by probabilistic counting method, PreProc. of 4th Fast Software Workshop (Jan. 1997). (The final version is appeared in LNCS 1267, pp.114-133.)
• K. Sakurai and Y. Zheng, ``Cryptographic weakness in the round transformation used in a block cipher with provable immunity against linear cryptanalysis,'' Proc. of 7th Annual International Symposium on Algorithms and Computation, LNCS 1178, pp.376-385 (Dec. 1996).
• K. SAKURAI, H. Shizuya, and M. Yung ``A progress report on subliminal-free channels,'' Proc. of Information Hiding Workshop, LNCS 1174 (1996), pp.157-168. %Aug. 1996.
• M. Burmester, Y.Desmedt, T. Itoh, K. SAKURAI, H. Shizuya, and M. Yung ``A progress report on subliminal-free channels,'' Proc. of Information Hiding Workshop, LNCS 1174 (1996), pp.157-168.
• K. Sakurai and Yoshinori Yamane, ``Blind decoding, blind undeniable signatures, and their applications to privacy protection,'' Proc. of Information Hiding Workshop, LNCS 1174 (1996), pp.257-264.
• M.Mambo, K.Sakurai, and E.Okamoto, ``How to utilize the transformability of digital signatures for solving the oracle problem,'' Advances in Cryptology -- Asiacrypt'96, LNCS 1163, 322-333 (Nov. 1996).
• K.Sakurai, ``A hidden cryptographic assumption in no-transferable identification schemes,'' Advances in Cryptology -- Asiacrypt'96, LNCS 1163, pp.159-172 (Nov.1996)
• Akio Yanbe and Kouichi Sakurai, ``On the complexity of computational problems associated with simple stochastic games,'' Proc. of 2st International Computing and Combinatorics Conference, LNCS 1090, pp.310-322.
• K.Sakurai, ``On separating proofs of knowledge from proofs of membership of languages and its application to secure identification scheme,'' Proc. of 1st International Computing and Combinatorics Conference, LNCS 959, pp.496-509.
• K.Sakurai and H. Shizuya, ``Relationships among the computational powers of breaking discrete log cryptosystems.'' Advances in Cryptology -- EUROCRYPT'95, LNCS 921, pp.341-355.
• K.Sakurai and T.Itoh, ``Subliminal channels for signature transfer and their application to signature distribution scheme,'' Advances in Cryptology -- Auscrypt'92, LNCS 718.
• K.Sakurai and T.Itoh, ``On bit correlations among preimages of 'many to one' one-way functions,'' Advances in Cryptology -- Auscrypt'92, LNCS 718.
• K.Sakurai and T.Itoh, ``On the discrepancy between the serial and the parallel of zero-knowledge protocols,'' Advances in Cryptology -- Crypto'92, LNCS 740.
• T.Okamoto, K.Sakurai and H.Shizuya, ``How intractable is the discrete logarithm for a general finite group ?,'' Advances in Cryptology -- EUROCRYPT'92, LNCS 658 (1993).
• T.Okamoto and K.Sakurai, ``Efficient algorithms for the construction of hyperellipitic cryptosystems,'' Advances in Cryptology -- Crypto'91, LNCS 576 (1992).
• T. Itoh, K.Sakurai and H. Shizuya ``Any language in IP has a divertible ZKIP,'' Advances in Cryptology -- Asiacrypt'91, LNCS 739 (1993).
• T.Itoh and K.Sakurai, ``On the complexity of constant round ZKIP of Possession of knowledge,'' Advances in Cryptology -- Asiacrypt'91, LNCS 739 (1993).
• T. Saito, K. Kurosawa, and K.Sakurai, ``4-move perfect ZKIP of knowledge with no assumption,'' Advances in Cryptology -- Asiacrypt'91, LNCS 739 (1993)
• H.Shizuya, T.Itoh, and K.Sakurai, ``On the complexity of hyperelliptic discrete logarithm problem,'' Advances in Cryptology -- EUROCRYPT'91, LNCS, 547 (1991)