Applications and Techniques in Information Security


Prof Kouichi Sakurai

Professor Kouichi SAKURAI
Kyushu University and Institute of Systems & Information Technologies and Nanotechnologies

Revisiting Identity-based encryption towards no-escrow: Application and analysis of Embedding Secret Key Information in RSA moduli

This talk first surveys existing approaches of Identity-based encryption schemes mainly based on the public key N = pq including RSA. Also we discuss the escrow problem associated with such IBE schemes, and consider how to fight against this escrow. We develop a new method to prevent impersonations of a public key owner by extending the existing technique to embed the information in the public key. Furthermore, we apply our method to design an anonymous encryption scheme. Also we report on further analysis of Lenstra's algorithm of embedding secret information into RSA moduli . (This is joint work with Motiki KITAHARA, Takanori YASUDA and Takashi NISHIDE.)

Kouichi Sakurai received the B.S. degree in mathematics from the Faculty of Science, Kyushu University in 1986. He received the M.S. degree in applied science in 1988, and the Doctorate in engineering in 1993 from the Faculty of Engineering, Kyushu University.

He was engaged in research and development on cryptography and information security at the Computer and Information Systems Laboratory at Mitsubishi Electric Corporation from 1988 to 1994. From 1994, he worked for the Dept. of Computer Science of Kyushu University in the capacity of associate professor, and became a full professor there in 2002.

He is concurrently working also with the Institute of Systems & Information Technologies and Nanotechnologies, as the chief of Information Security laboratory, for promoting research co-oporations among the industry, university and government under the theme "Enhancing IT-security in social systems". He has been successful in generating such co-operation between Japan, China and Korea for security technologies as the leader of a Cooperative International Research Project supported by the National Institute of Information and Communications Technology (NICT) during 2005-2006. Moreover, in March 2006, he established research co-oporations under a Memorandum of Understanding in the field of information security with Professor Bimal Kumar Roy, the first time Japan has partnered with The Cryptology Research Society of India (CRSI).

Professor Sakurai has published more than 200 academic papers around cryptography and information security (See:


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