# Noboru Kunihiro

Last update 2017/06/27

Japanese version is here.

Affiliation/Position:: Associate Professor, The University of Tokyo

Department of Complexity Science and Engineering, Graduate School of Frontier Sciences

### Employment:

- Mar. 2008 - now Associate Professor, University of Tokyo, Japan
- Apr. 2006 - Feb. 2008 Associate Professor, University of Electro-Communications, Japan
- Jul.2002 - Mar.2006 Assistant Professor, University of Electro-Communications, Japan
- Apr.1996 - Jun.2002 Researcher, NTT Laboratories, Japan

### Education:

- Jan. 2002 Ph.D. from University of Tokyo
- Apr.1994 - Mar.1996, The University of Tokyo, Japan
- Master of Engineering (M.E. in Mathematical Engineering)

- Apr.1990- Mar.1994 The University of Tokyo, Japan
- Bachelor of Engineering (B.E.in Mathematical Engineering)

### Dissertation

- Title: Security and Efficiency Analyses of Public Key Cryptosystems
- Ph.D. from University of Tokyo

## Selected Publications:

- See also DBLP.

### IACR Conference & Workshop

- Adversary-dependent Lossy Trapdoor Function from Hardness of Factoring Semi-smooth RSA Subgroup Moduli, by T. Yamakawa, S. Yamada, G. Hanaoka, and N. Kunihiro, in Proc. of CRYPTO2016, LNCS 9815, pp. 3--32, 2016.
- How to Generalize RSA Cryptanalyses, by A. Takayasu and N. Kunihiro, in Proc. of PKC2016, LNCS9615, pp. 67--97, 2016.
- RSA meets DPA: Recovering RSA Secret Keys from Noisy, by N. Kunihiro and J. Honda, in Proc. of CHES2014, LNCS 8731, pp. 261-278, 2014.
- Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications, by Takashi Yamakawa; Shota Yamada; Goichiro Hanaoka; Noboru Kunihiro, in Proc. of CRYPTO2014 (2) LNCS 8617, pp. 90-107, 2014.
- A Framework and Compact Constructions for Non-monotonic Attribute-Based Encryption, by Shota Yamada, Nuttapong Attrapadung, Goichiro Hanaoka, Noboru Kunihiro, in Proc. of PKC2014, LNCS 8383, pp. 275-292, 2014.
- Recovering RSA Secret Keys from Noisy Key Bits with Erasures and Errors, by Noboru Kunihiro, Naoyuki Shinohara and Tetsuya Izu, in Proc. of PKC2013, LNCS 7778, pp. 180-197, 2013.
- Space Efficient Signature Schemes from the RSA Assumption, by Shota Yamada and Goichiro Hanaoka and Noboru Kunihiro, in Proc. of PKC2012, LNCS7178, pp. 260-277, 2012.
- Verifiable Predicate Encryption and Application to CCA Security and Anonymous Predicate Authentication, by Shota Yamada and Nuttapong Attrapadung and Bagus Santoso and Goichiro Hanaoka and Jacob C.N. Schuldt and Noboru Kunihiro, in Proc. of PKC2012, LNCS7178, pp. 349-364, 2012.
- Generic Constructions for Chosen-Ciphertext Secure Attribute Based Encryption, by Shota Yamada, Nuttapong Attrapadung, Goichiro Hanaoka and Noboru Kunihiro, in Proc. of PKC2011, LNCS6571, pp. 71-89, 2011.
- New Key Recovery Attack on HMAC/NMAC-MD4 and NMAC-MD5, by Lei Wang and Kazuo Ohta and Noboru Kunihiro, in Proc. of Eurocrypt2008, LNCS4965, pp. 237-253, 2008.
- Deterministic Polynomial Time Equivalence between Factoring and Key-Recovery Attack on Takagi's RSA, by Noboru Kunihiro and Kaoru Kurosawa, in Proc. of PKC2007, LNCS4450, pp. 412-425, April 16-20, Beijing, China.
- New Message Difference for MD4, by Y. Sasaki, L. Wang, K. Ohta and N. Kunihiro, in Proc. of FSE 2007, LNCS4593, pp. 329-348, March 26-28, 2007, Luxembourg.
- Improved Collision Search for SHA-0, by Yusuke Naito, Yu Sasaki, Takeshi Shimoyama, Jun Yajima, Noboru Kunihiro and Kazuo Ohta, in Proc. of Asiacrypt2006, LNCS 4284, pp. 21-36, December 3-7, 2006, Shanghai, China.
- Modulus Search for Elliptic Curve Cryptosystems, by Koyama K., Tsuruoka Y. and Kunihiro, N., in Advances in Cryptology -- Asiacrypt'99, LNCS 1716, pp. 1-7 (1999).
- Equivalence of Counting the Number of Points on Elliptic Curve over the ring $Z_n$ and Factoring $n$, by Noboru Kunihiro and Kenji Koyama, In Proceeding of Advances in Cryptology -- EUROCRYPT'98, LNCS 1403, pp. 47-58 (1998).

### Other (Selected) Conferences (ACNS, ACISP, AsiaCCS, CT-RSA, SAC, SCN, FC)

- Bounds in Various Generalized Settings of the Discrete Logarithm Problem, by Jason Ying and Noboru Kunihiro, in Proc. of ACNS2017, LNCS 10355, pp. 498-517, 2017.
- Improved Factoring Attacks on Multi-Prime RSA with Small Prime Difference, by Mengce Zheng, Noboru Kunihiro and Honggang Hu, in Proc. of ACSISP2017, LNCS 10342, pp. 324-342, 2017.
- Mis-operation Resistant Searchable Homomorphic Encryption, by Keita Emura, Takuya Hayashi, Noboru Kunihiro and Jun Sakuma, in Proc. of ASIA CCS'17, pp. 215--229, 2017.
- Improved Key Recovery Algorithms from Noisy RSA Secret Keys with Analog Noise, by Noboru Kunihiro and Yuki Takayasu, in Proc. of CT-RSA2017, LNCS 10159, pp. 328--343, 2017.
- A Tool Kit for Partial Key Exposure Attacks on RSA, by A. Takayasu and N. Kunihiro, in Proc. of CT-RSA2017, LNCS 10159, pp. 58--73, 2017.
- Partial Key Exposure Attacks on RSA with Multiple Exponent Pairs, by A. Takayasu and N. Kunihiro, in Proc. of ACISP2016, LNCS 9723, pp. 243--257, 2016.
- Generalized Hardness Assumption for Self-bilinear Map with Auxiliary Information, by T. Yamakawa, G. Hanaoka and N. Kunihiro, in Proc. of ACISP2016, LNCS 9723, pp. 269--284, 2016.
- Private Information Retrieval with Preprocessing Based on the Approximate GCD Problem, by T. Vannet and N. Kunihiro, in Proc. of SAC2015, LNCS 9566, pp. 227--240, 2015.
- Partial Key Exposure Attacks on CRT-RSA: Better Cryptanalysis to Full Size Encryption Exponents, by A. Takayasu and N. Kunihiro, in Proc. of ACNS2015, LNCS 9092, 2015.
- Chosen Ciphertext Security on Hard Membership Decision Groups: The Case of Semi-smooth Subgroups of Quadratic Residues, by Takashi Yamakawa, Shota Yamada, Koji Nuida, Goichiro Hanaoka and Noboru Kunihiro, in Proc. of SCN2014, LNCS 8642, pp. 558-577, 2014.
- Partial Key Exposure Attacks on RSA: Achieving Boneh-Durfee's Bound, by A. Takayasu and N. Kunihiro, in Proc. of SAC2014, LNCS 8781, pp. 345-362, 2014.
- Cryptanalysis of RSA with Multiple Small Secret Exponents, by A. Takayasu and N. Kunihiro, in Proc. of ACISP2014, LNCS 8544, pp. 176-191, 2014.
- Better Lattice Constructions for Solving Multivariate Linear Equations Modulo Unknown Divisors, by Atsushi Takayasu and Noboru Kunihiro, in Proc. of ACISP2013, LNCS 7959, pp. 118-135, 2013.
- Optimal Bounds for Multi-Prime Phi-Hiding Assumption, by Kaori Tosu, Noboru Kunihiro, in Proc. of ACISP2012, LNCS7372, pp. 1-14, 2012.
- Faster Algorithm for Solving Hard knapsacks for Moderate Message Length, by Yuji Nagashima, Noboru Kunihiro, in Proc. of ACISP2012, LNCS7372, pp. 43-56, 2012.
- Two-Dimensional Representation of Cover Free Families and its Applications: Short Signatures and More, by Shota Yamada, Goichiro Hanaoka, and Noboru Kunihiro, in Proc. of CT-RSA2012, 7178, pp. 260-277, 2012.
- Generic Construction of Chosen Ciphertext Secure Proxy Re-Encryption, by Goichiro Hanaoka, Yutaka Kawai, Noboru Kunihiro, Takahiro Matsuda, Jian Weng, Rui Zhang, Yunlei Zhao in Proc. of CT-RSA2012, 7178, pp. 349-364, 2012.
- A Unified Framework for Small Secret Exponent Attack on RSA, by Noboru Kunihiro, Naoyuki Shinohara and Tetsuya Izu, in Proc. of SAC2011, LNCS7118, pp. 260-277, 2011.
- Solving Generalized Small Inverse Problems, by N. Kunihiro in Proc. of ACISP2010, LNCS6168, pp. 248-263, 2010.
- Security of MD5 Challenge and Response: Extension of APOP Password Recovery Attack, by Yu Sasaki, Lei Wang, Kazuo Ohta and Noboru Kunihiro , in Proc. of CT-RSA2008, LNCS4964, pp. 1-18, 2008.
- Small Secret Key Attack on a variant of RSA (due to Takagi), by Kouichi Itoh and Noboru Kunihiro and Kaoru Kurosawa, in Proc. of CT-RSA2008, LNCS4964, pp. 387-406, 2008.
- Password Recovery Attack on Authentication Protocol MD4(Password||Challenge), by Lei Wang and Kazuo Ohta and Noboru Kunihiro, in Proc. of ASIACCS2008, pp. 3-9, 2008.
- A Strict Evaluation Method on the Number of Conditions for the SHA-1 Collision Search, by Jun Yajima, Terutoshi Iwasaki, Yusuke Naito, Yu Sasaki, Takeshi Shimoyama, Noboru Kunihiro, Kazuo Ohta, in Proc. of ASIACCS2008, pp. 10-20, 2008.
- A New Strategy for Finding a Differential Path of SHA-1, by Jun Yajima, Yu Sasaki, Yusuke Naito, Terutoshi Iwasaki, Takeshi Shimoyama, Noboru Kunihiro, Kazuo Ohta, in Proc. of ACISP 2007, LNCS4586, pp. 45-58, July, 2007.
- Provable Secure Electronic Cash based on Blind Multisignature schemes, by Y. Hanatani, Y. Komano, K. Ohta and N. Kunihiro, in Financial Cryptography'06, LNCS 4107, pp. 236-250, Feb.27-March 2, 2006,

### Journal Papers (in English)

- Constructing Subspace Membership Encryption through Inner Product Encryption, by Shuichi Katsumata and Noboru Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E100-A, No.9, pp. 1804--1815, 2017.
- Self-bilinear Map on Unknown Order Groups from Indistinguishability Obfuscation and Its Applications, by Takashi Yamakawa, Shota Yamada, Goichiro Hanaoka, and Noboru Kunihiro, Algorithmica, 79 (4), pp. 1286-1317, 2017. DOI: 10.1007/s00453-016-0250-8.
- General Bounds for Small Inverse Problems and Its Applications to Multi-Prime RSA, by Atsushi Takayasu and Noboru Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E100-A, No.1, pp. 50--61, 2017.
- Searchable symmetric encryption capable of searching for an arbitrary string, by Y. Uchide and N. Kunihiro, Security and Communication Networks, vol. 9, issue 12, pp. 1726--1736, 2016.
- A limitation on security evaluation of cryptographic primitives with fixed keys, by Y. Kawai, G. Hanaoka, K. Ohta and N. Kunihiro, Security and Communication Networks, vol. 9, issue 12, pp. 1663--1675, 2016.
- Security Analysis on AUTH Protocol and Its Variant against the Man-in-the-Middle Attack, by K. Endo and N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E98-A, No.1, pp. 153-161, 2015.
- Better Lattice Constructions for Solving Multivariate Linear Equations Modulo Unknown Divisors, by A. Takayasu and N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E97-A, No.6, pp. 1259--1272, 2014.
- Recovering RSA Secret Keys from Noisy Key Bits with Erasures and Errors, by N. Kunihiro, N. Shinohara and T. Izu, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E97-A, No.6, pp. 1273--1284, 2014.
- A Unified Framework for Small Secret Exponent Attack on RSA, by N. Kunihiro, N. Shinohara and T. Izu, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E97-A, No.6, pp. 1285--1295, 2014.
- Secret handshake scheme with request-based-revealing, by Yutaka Kawai, Noboru Kunihiro, Computers \& Mathematics with Applications 65(5), pp. 786-798, 2013.
- Random Sampling Reduction with Precomputation, by Masayuki YOSHINO and Noboru KUNIHIRO, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E96-A, No.1, pp. 150--157, 2013.
- On the Hardness of Subset Sum Problem from Different Intervals, by Jun KOGURE Noboru KUNIHIRO Hirosuke YAMAMOTO, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E95-A, No.5, pp. 903--908, 2012.
- On the (Im)possibility Results for Strong Attack Models for Public Key Cryptsystems, by Yutaka Kawai, Yusuke Sakai, Noboru Kunihiro, Special issue in the Journal of Internet Services and Information Security, Vol. 1, No. 2/3, pp. 125-139, 2011.
- Solving Generalized Small Inverse Problems, by N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E94-A, No.6, pp. 1274-1284, 2011.
- Small Secret CRT-Exponent Attacks on Takagi's RSA, by Naoyuki SHINOHARA, Tetsuya IZU and Noboru KUNIHIRO, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E94-A, No.1, pp. 19-27, 2011.
- Public Key Encryption Schemes from the (B)CDH Assumption with Better Efficiency, by Shota YAMADA Yutaka KAWAI Goichiro HANAOKA Noboru KUNIHIRO, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E93-A, No.11, pp. 1984--1993, 2010.
- Quantum addition circuits and unbounded fan-out, by Yasuhiro Takahashi, Seiichiro Tani, and Noboru Kunihiro, Quantum Information and Computation, Vol.10 No.9/10, pp.872--890, 2010.
- New Conditions for Secure Knapsack Schemes against Lattice Attack, by N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E93-A, No.6, pp. 1058--1065, 2010.
- Extension of Secret Handshake Protocols with Multiple Groups in Monotone Condition, by Y. Kawai, S. Tanno, T. Kondo, K. Yoeneyama, K. Ohat and N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E93-A, No.6, pp. 1122--1131, 2010.
- Cryptanalysis of Two MD5-Based Authentication Protocols: APOP and NMAC, by Lei Wang, Kazuo Ohta, Yu Sasaki, Kazuo Sakiyama and Noboru Kunihiro, IEICE TRANSACTIONS on Information and Systems, Vol. E93-D, No. 5, pp. 1087--1095, 2010.
- Practical Password Recovery Attacks on MD4 Based Prefix and Hybrid Authentication Protocols, by Yu Sasaki, Lei Wang, Kazuo Ohta, Kazumaro Aoki and Noboru Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E93-A, No.1, pp. 84--92, 2010.
- Small Secret Key Attack on a Takagi's Variant of RSA, by Kouichi Itoh, Noboru Kunihiro and Kaoru Kurosawa, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E92-A, No.1, pp. 33--41, 2009.
- Near-Collision Attacks on MD4: Applied to MD4-Based Protocols, by Lei Wang, Kazuo Ohta and Noboru Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E92-A, No.1, pp. 76--86, 2009.
- A Strict Evaluation on the Number of Conditions for SHA-1 Collision Search, by Jun Yajima, Terutoshi Iwasaki, Yusuke Naito, Yu Sasaki, Takeshi Shimoyama, Thomas Peyrin, Noboru Kunihiro and Kazuo Ohta, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E92-A, No.1, pp. 87--95, 2009.
- Extended Password Recovery Attacks against APOP, SIP, and Digest Authentication, by Yu Sasaki, Lei Wang, Kazuo Ohta and Noboru Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E92-A, No.1, pp. 96--104, 2009.
- Deterministic Polynomial Time Equivalence between Factoring and Key-Recovery Attack on Takagi's RSA, by Noboru Kunihiro and Kaoru Kurosawa, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E91-A, No.9, pp. 2356--2364, 2008.
- A Fast Quantum Circuit for Addition with Few Qubits, by Yasuhiro Takahashi and Noboru Kunihiro, Quantum Information and Computation, Vol.8 No.6/7, pp.636--649, 2008.
- Improved Collision Search for Hash Functions: New Advanced Message Modification, by Yusuke NAITO Kazuo OHTA Noboru KUNIHIRO, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E91-A, No.1, pp. 46--54, 2008.
- New Message Differences for Collision Attacks on MD4 and MD5, by Yu SASAKI Lei WANG Noboru KUNIHIRO Kazuo OHTA, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E91-A, No.1, pp. 55--63, 2008.
- Factorization of Square-Free Integers with High Bits Known, by Bagus SANTOSO Noboru KUNIHIRO Naoki KANAYAMA Kazuo OHTA, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E91-A, No.1, pp. 306--315, 2008.
- Provably Secure Untraceable Electronic Cash against Insider Attacks, by Y. Hanatani, Y. Komano, K. Ohta and N. Kunihiro, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E90-A, No.5, pp. 980--991, 2007.
- The quantum Fourier transform on a linear nearest neighbor architecture, by Yasuhiro Takahashi, Noboru Kunihiro and Kazuo Ohta, Quantum Information and Computation, Vol.7 No.4, pp.383--391, 2007.
- Improved Collision Attacks on MD4 and MD5, by Y. SASAKI, Y. NAITO, N. KUNIHIRO and Kazuo OHTA IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E90-A, No.1, pp. 36--47 (2007).
- Maurer-Yacobi ID based Key Distribution Revisited, by N. Kunihiro W. Abe and K. Ohta, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E89-A, No.5, pp. 1421--1424, 2006.
- Visual Secret Sharing Schemes for Multiple Secret Images Allowing the Rotation of Shares, by M. Iwamoto, L. Wang, K. Yoneyama, N. Kunihiro and K. Ohta, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E89-A, No.5, pp. 1382--1395 (2006)
- A quantum circuit for Shor's factoring algorithm using 2n+2 qubits, by Yasuhiro Takahashi and Noboru Kunihiro, Quantum Information and Computation, Vol.6 No.2, pp.184--192, 2006.
- A LINEAR-SIZE QUANTUM CIRCUIT FOR ADDITION WITH NO ANCILLARY QUBITS, by Yasuhiro Takahashi and Noboru Kunihiro, Quantum Information and Computation, Vol.5 No.6, pp.440--448, 2005.
- Exact Analyses of Computational Time for Factoring in Quantum Computers, by N. Kunihiro IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E88-A, No.1, pp. 105--111 (2005)
- Efficient Algorithms for NMR Quantum Computers with Small Qubits, by Noboru KUNIHIRO and Shigeru YAMASHITA, New Generation Computing Vol. 21, No. 4, pp.329--337, 2003.
- A Quantum Algorithm using NMR Computers to Break Secret-Key Cryptosystems, by Kazuo OHTA, Tetsuro NISHINO, Seiya OKUBO and Noboru KUNIHIR, New Generation Computing Vol. 21, No. 4, pp.347--361, 2003.
- Two Discrete Log Algorithms for Super-Anomalous Elliptic Curves and Their Applications, by Kunihiro, N. and Koyama, K., IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E83-A, No.1, pp. 10--16, 2000.
- New methods for generating short addition chains, by Kunihiro, N. and Yamamoto, H, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E83-A, No.1, pp. 60--67, 2000.
- Window and Extended Window methods for Addition chain and Addition-Subtraction chain, by Kunihiro, N. and Yamamoto, H., IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E81-A, No.1, pp. 72--81, 1998.

## Advising

### Graduated PhD Students (8)

- Jason Ying, Atsushi Takayasu, Takashi Yamakawa, Thomas Vannet, Shota Yamada, Masayuki Yoshino, Yutaka Kawai, Yasuhiro Takahashi

### Current PhD Students (2)

- Shuichi Katsumata, Ken Naganuma

## Professional Activities

### Program Chair

- IWSEC2010 Program co-Chair (2010.11)

### Program Committee:

- ISITA2004 Technical Program Committee (2004.10)
- 3rd International IEEE Security in Storage Workshop Program Committee (2005.12)
- TQC2006 Program Committee (2006.02)
- ISITA2006 Technical Program Committee (2006.10)
- IWSEC2006 Program Committee (2006.10)
- MCIS International Progaram Committee(2006.11)
- TQC2007 Program Committee (2007.01)
- IWSEC2007 Program Committee (2007.10)
- IWSEC2008 Program Committee (2008.11)
- ISITA2008 Technical Program Committee (2008.12)
- IWSEC2009 Program Committee (2009.10)
- ProvSec2010 Program Committee (2010.10)
- ProvSec2011 Program Committee (2011.10)
- IWSEC2011 Program Committee (2011.11)
- ISITA2012 Technical Program Committee (2012.10)
- IWSEC2012 Program Committee (2012.11)
- PKC2013 Program Committee (2013.02)
- IWSEC2013 Program Committee (2013.11)
- IWSEC2014 Program Committee (2014.08)
- ISITA2014 Technical Program Committee (2014.10)
- IWSEC2015 Program Committee (2015.08)
- ACISP2016 Program Committee (2016.07)
- ISITA2016 Technical Program Committee (2016.10)
- IWSEC2017 Program Committee (2017.08)
- ACISP2017 Program Committee (2017.07)
- ISC2017 Program Committee (2017.11)
- ISPEC2017 Program Committee (2017.12)

### Address:

- Bldg. of Transdisciplinary Sciences Department of Complexity Science and Engineering School of Frontier Sciences, University of Tokyo 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8561, Japan
- e-mail: kunihiro (at) k.u-tokyo.ac.jp