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1) General secret sharing schemes using hierarchical threshold scheme, IEICE Transaction on Fundamentals, E102-A, No. 9, pp. 1037-1047, Sep. 2019.Improvement of general secret sharing scheme reducing shares distributed to specified participants, IEICE Transaction on Fundamentals, E102-A, No. 6, pp. 808-817, Jun. 2019.2) 3) Recursive general secret sharing scheme based on authorized subsets, International Journal of Machine Learning and Computing (IJMLC), Vol. 9, No. 1, pp. 75-82, Jan. 20194) New general secret sharing scheme based on unauthorized subsets: improvement of information rates for specified participants, Journal of Information Processing, Vol. 24, No.5, pp. 772-780, Sep. 2016.5) Efficient secret sharing schemes realizing general access structures, IEICE Transaction on Fundamentals, E87-A, No. 7, pp. 1788-1797, Jul. 2004.Kouya Tochikubo is a professor in the Department of Mathematical Information Engineering, College of Industrial Technology, Nihon University. He received his BSc degree from Tokyo University of Science, his MSc degree from Japan Advanced Institute of Science and Technology (JAIST) and his DEng degree from Tokyo Institute of Technology in 1996, 1998, and 2004, respectively. He joined the Systems Integration Technology Center, Toshiba Corporation in 1998. He was a visiting professor at the University of Waterloo from 2012 to 2013. His research interests are information theory and information security. Dr. Tochikubo is a member of the Institute of Electronics, Information and Communication Engineers (IEICE) and the Information Processing Society of Japan (IPSJ). He received the SCIS Paper Award and the IEICE Best Paper Award in 2002 and 2005, respectively.－　　－28Research AchievementsKouya TOCHIKUBOProfessor, Department of Mathematical Information Engineering