The safety problem is the one to determine whether or not a given subject can eventually obtain an access privilege to a given object. Generally speaking, unfortunately, the safety problem is undecidable. Little is known about protection systems where the safety problem is decidable, except for strongly constrained systems (e.g., monotonic systems).
Therefore, I have studied decidability of the safety problem for non-monotonic protection systems and successfully showed that it becomes decidable in some cases. In my subsequent research, I will go on to investigate decidability of the problem for non-monotonic systems on which less restrictions are imposed.
As mentioned above, because it is (in terms of computational complexity) extremely hard to analyze the behavior of access matrix models, in reality it is often the case that information flow control is enforced in addition to ordinary access control. In that case, it is likely that information leakage may occur through channels which are not normally supposed to transfer information between objects (such channels are called `covert channels.') In order to identify and rule out such channels, we have to formally specify security requirements of a system and accordingly develop the system that satisfies the specification. Non-interference security model can be used for that purpose. However, the model is not intuitive and has the disadvantage that it is difficult to design and develop systems based on the model. Consequently I am interested in devising a non-interference model that has no such difficulties.
In today's computer networks, it is one of the utmost concerns to provide anonymity for protecting users' privacy. However previous anonymous communication protocols have such disadvantages that prohibitive computational cost for repeated encryption is imposed, or that receiver anonymity is not achieved.
Therefore, we have proposed a new anonymous communication scheme with cyclic routes. Cyclic routes have a desirable feature that there exist neither starting points nor end points. This feature is quite useful to realize anonymous communication where identities of senders (starting points) and receivers (end points) must be made unknown. Thus our scheme reduces the cost of key distribution, encryption, and decryption, maintaining anonymity of both senders and receivers.
Software obfuscation, which transforms programs into the form that is hard to understand and tamper illegally, is a promising approach for protection of intellectual property rights of software in untrusted environments. Unfortunately most of previous obfuscation techniques do not have a theoretical basis and thus it is unclear how effective they are. Therefore I have studied new software obfuscation techniques, which are based on the difficulty of interprocedural analysis. The essence of the obfuscation techniques is a new complexity problem to precisely determine the address a function pointer points to in the presence of arrays of function pointers. The problem can be shown to be NP-hard and hence the fact provides a theoretical basis for the obfuscation techniques. Furthermore, we have already implemented a prototype obfuscation tool that obfuscates C programs according to the proposed techniques. Some of the experimental results can be found in our papers.
Classical computer systems are now approaching to the limits with respect to an areal size of a computational bit, tolerable heat emission, and performance. Therefore, quantum computation has recently been attracting so much interest, since it is expected to solve these problems. For example, the postulates of quantum mechanism are reversible and so quantum computation can be done without heat emission, at least in theory. Unfortunately, due to several technological obstacles, it is said that at best it will take a few decades before quantum computers are actually realized, although, quantum communication systems are now being into a practical use. Therefore I have been doing research in the area of quantum computation, quantum protocols (especially quantum coin flipping protocols), and quantum communication systems.
In recent years the Internet has been exposed to a serious threat of DoS (denial of service) attacks. Therefore, widespread attention has been paid to IP traceback schemes, which try to identify the initiator who has mounted the attacks. I am in particular interested in developing theories and architectures of efficient IP traceback technology.
In recent years, more and more computers become interconnected through computer networks and the establishment of security of a proper level in such environments is of critical importance.
To this end, I considered an agent-oriented architecture as a promising computing paradigm for such environments and have studied security models and mechanisms for it. My research interest is to incorporate those results into a new security architecture in open distributed environments.
Yuta Kurihara and Masakazu Soshi. A Novel Hash Chain Construction for Simple and Efficient Authentication. In 14th Annual Conference on Privacy, Security and Trust, PST 2016, December 2016.
Kayoko Iwamoto, Masakazu Soshi, and Takashi Satoh. An efficient and adaptive IP traceback scheme. In IEEE International Workshop on Internet of Things Services (IoTS), pp. 235-240, November 2014.
Tomoyuki Karasawa, Masakazu Soshi, and Atsuko Miyaji. A novel hybrid IP traceback scheme with packet counters. In The 5th International Conference on Internet and Dsitributed Computing Systems (IDCS 2012), volume 7646 of Lecture Notes in Computer Science, pp.71-84. Springer-Verlag, 2012.
Atsushi Waseda and Masakazu Soshi. Consideration for multi-threshold multi-secret sharing schemes. In International Symposium on Information Theory and Applications (ISITA 2012), pp.265-269, August 2012.
Masakazu Soshi and Atsushi Waseda. On Efficient Construction of One Time Signatures. (In Japanese) IPSJ SIG Technical Reports, 2012-CSEC-56, No.35, March, 2012.
Keita Emura, Atsuko Miyaji, Akito Nomura, Mohammad Shahriar Rahman, and Masakazu Soshi. Ideal secret sharing schemes with share selectability. (link to pdf) In The 13th International Conference on Information and Communications Security (ICICS 2011), volume 7043 of Lecture Notes in Computer Science, pp. 143-157. Springer-Verlag, 2011.
Atsuko Miyaji, Mohammad Shahriar Rahman, and Masakazu Soshi. Efficient and low-cost RFID authentication schemes. (link to pdf) Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications (JoWUA), Vol. 2, No. 3, pp. 4-25, 2011.
Atsuko Miyaji, Mohammad Shahriar Rahman, and Masakazu Soshi. Hidden credential retrieval without random oracles. (link to pdf) In The 11th International Workshop on Information Security Applications (WISA 2010), volume 6513 of Lecture Notes in Computer Science, pp.160-174. Springer-Verlag, 2010.
Keita Emura, Atsuko Miyaji, Akito Nomura, Kazumasa Omote, and Masakazu Soshi. A ciphertext-policy attribute-based encryption scheme with constant ciphertext length. (link to pdf) International Journal of Applied Cryptography (IJACT), Vol. 2, No. 1, pp.46-59, 2010.
Keita Emura, Atsuko Miyaji, Akito Nomura, Kazumasa Omote, and Masakazu Soshi. A ciphertext-policy attribute-based encryption scheme with constant ciphertext length. (link to pdf) In The 5th Information Security Practice and Experience Conference (ISPEC 2009), volume 5451 of Lecture Notes in Computer Science, pp.13-23. Springer-Verlag, April 2009.
Rahman Mohammad Shahriar, Masakazu Soshi, and Atsuko Miyaji. A secure RFID authentication protocol with low communication cost. (link to pdf) In The 3rd International Workshop on Intelligent, Mobile and Internet Services in Ubiquitous Computing (IMIS 2009), pp.559-564, March 2009.
Atsushi Waseda, Takayuki Takagi, Masakazu Soshi, and Atsuko Miyaji. Quantum secret sharing between multiparty and multiparty against the attacks with single photons or EPR-pair. In International Symposium on Information Theory and Applications (ISITA 2008), December 2008.
Wataru Hasegawa, Masakazu Soshi, and Atsuko Miyaji. Mobile agent security with efficient oblivious transfer. In International Conference on Security and Cryptography (SECRYPT 2007), pp.299-304, July 2007.
Atsushi Waseda, Masakazu Soshi, and Atsuko Miyaji. Consideration for quantum multi-secret sharing. (In Japanese) (link to pdf) IPSJ Journal, Vol.48, No.7, pp.2447-2464, July 2007.
Takeaki Terada, Masakazu Soshi, and Atsuko Miyaji. An IP traceback scheme with variably probabilistic packet marking. In International Symposium on Information Theory and Applications (ISITA 2006), October 2006.
Atsushi Waseda, Masakazu Soshi, and Atsuko Miyaji. Quantum coin flipping protocol using n-dimensional quantum states. (In Japanese) (link to pdf) IPSJ Journal, Vol.46, No.8, pp.1903-1911, August 2005.
Yusuke Sakabe, Masakazu Soshi, and Atsuko Miyaji. Java obfuscation - approaches to construct tamper-resistant object-oriented programs. IPSJ Journal, Vol.46, No.8, pp.2107-2119, August 2005.
Atsushi Waseda, Masakazu Soshi, and Atsuko Miyaji. n-state quantum coin flipping protocol. In International Conference on Information Technology (ITCC), volume II, pp.776-777, 2005.
Takeaki Terada, Masakazu Soshi, and Atsuko Miyaji. A new pushback mechanism resistant to DDoS attacks. In 2004 International Symposium on Information Theory and Applications (ISITA 2004), October 2004.
Shigeki Kitazawa, Masakazu Soshi, and Atsuko Miyaji. On anonymity metrics for practical anonymous communication protocols. IPSJ Journal, Vol.45, No.8, pp.1887-1897, August 2004.
Takeaki Terada, Masakazu Soshi, and Atsuko Miyaji. Toward modeling of a pushback mechanism. IPSJ Journal, Vol.45, No.8, pp.1948-1953, August 2004. (In Japanese).
Atsushi Waseda, Masakazu Soshi, and Atsuko Miyaji. A proposal of quantum coin tossing using n-states. Technical Report of IEICE, ISEC 2004-10 (2004-05), pp. 65-68, May 2004.
Masakazu Soshi, Mamoru Maekawa, and Eiji Okamoto. The dynamic-typed access matrix model and decidability of the safety problem. IEICE Transactions on Fundamentals, Vol.E87-A, No.1, pp.190-203, January 2004.
Yusuke Sakabe, Masakazu Soshi, and Atsuko Miyaji. Java obfuscation with a theoretical basis for building secure mobile agents. In Antonio Lioy and Daniele Mazzocchi, editors, Seventh IFIP TC-6 TC-11 Conference on Communications and Multimedia Security (CMS'03), volume 2828 of Lecture Notes in Computer Science, pp.89-103. Springer-Verlag, October 2003.
Shigeki Kitazawa, Masakazu Soshi, and Atsuko Miyaji. Evaluation of anonymity of practical anonymous communication networks. In Rei Safavi-Naini and Jennifer Seberry, editors, The Eighth Australasian Conference on Information Security and Privacy - ACISP 2003, volume 2727 of Lecture Notes in Computer Science, pp.13-26. Springer-Verlag, July 2003.
Sayaka Fukuda, Masakazu Soshi, and Atsuko Miyaji. A Consideration for the Bias of Quantum Coin Flipping - Extension to 4 States Protocol from 3 States. Technical Report of IEICE, ISEC 2003-4, pp.21-24, May 2003.
Toshio Ogiso, Yusuke Sakabe, Masakazu Soshi, and Atsuko Miyaji. Software obfuscation on a theoretical basis and its implementation. IEICE Transactions on Fundamentals, Vol.E86-A, No.1, pp.176-186, January 2003.
Hiroyuki Nishikawa, Atsuko Miyaji, Masakazu Soshi, and Toshio Omote. A secure and flexible digital contents building system. In 2002 International Symposium on Information Theory and Applications (ISITA 2002), October 2002, S6-1-4, pp.223-226.
Masakazu Soshi and Atsuko Miyaji. Labeled certificate: Flexible trust management of public key infrastructures. In 2002 International Symposium on Information Theory and Applications (ISITA 2002), October 2002, S6-1-2, pp.215-218.
Toshio Ogiso, Yusuke Sakabe, Masakazu Soshi, and Atsuko Miyaji. Software tamper resistance based on the difficulty of interprocedural analysis. In The Third International Workshop on Information Security Applications (WISA 2002), pp. 437-452, August 2002.
Shigeki Kitazawa, Masakazu Soshi, and Atsuko Miyaji: An agent-based model of anonymous communication protocols. Sixth International Workshop on Enterprise Security, 10th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprise, 2001.
Masakazu Soshi: Safety analysis of the dynamic-typed access matrix model. In Frederic Cuppens, Yves Deswarte, Dieter Gollmann, and Michael Waidner, editors, Computer Security - ESORICS 2000: 6th European Symposium on Research in Computer Security, volume 1895 of Lecture Notes in Computer Science, pp.106-121. Springer-Verlag, October 2000.
Shigeki Kitazawa, Masakazu Soshi, and Atsuko Miyaji. Anonymous communication with elementary cyclic routes. IPSJ Journal, Vol.41, No.8, pp.2148-2160, August 2000.
Tatsuya Yamada, Masakazu Soshi, and Atsuko Miyaji. The secure renewal of cryptosystems in the open network architecture. IPSJ Journal, Vol.41, No.8, pp.2102-2109, August 2000.
Masakazu Soshi, Takeharu Kato, and Mamoru Maekawa. An Access Control Model based on Dual Labels. Transactions of Information Processing Society of Japan, Vol. 40, No. 3, pp. 1305-1314, March 1999.
Masakazu Soshi, Takehrau Kato, and Mamoru Maekawa. Flexible Protection Realized by Proxies in Distributed Systems. Transactions of Information Processing Society of Japan, Vol. 39, No. 3, pp. 810-817, March 1998.
Masakazu Soshi and Mamoru Maekawa. A new authorization model and its mechanism using service paths in open distributed environments. Proceedings of IFIP TC6 WG 6.1 International Working Conference on Distributed Applications and Interoperable Systems (DAIS '97), pp.251-264, 1997.
Masakazu Soshi and Mamoru Maekawa. The Saga security system-a security architecture for open distributed systems. Proceedings of the 5th IEEE Workshop on Future Trends of Distributed Computing Systems, pp. 53-58, 1997.