I studied number theory at university, and drawing on the experience, I have been engaged in the research on cryptography, since I joined Hitachi, Ltd., Yokohama Laboratory. Information technology goes into use in social infrastructure, and the information security becomes a fundamental technique. Especially, the cryptography is the core technology. According to the diversification of requests from industry, deeper mathematics is required in order to study sophisticated cryptography. At present, I have interest in “private information processing” and homomorphic encryption schemes. More number theory and algebraic geometry are needed.