Research

Cryptography with Advanced Functionality

In conventional cryptography, there is only one specific person to whom a message can be sent. On the other hand, in functional encryption, one-to-many communication is possible. In other words, in functional encryption, the sender of a message can encrypt it in such a way that only a user who satisfies certain conditions can decrypt the ciphertext and recover the information. The conditions that can be specified are expressed in Boolean formulas such as "(department head or higher ∨ accounting department) ∧ head office affiliation". Also, in situations such as pay-per-view broadcasting, it is necessary to encrypt and distribute information simultaneously to many users who are qualified to receive it. Using a primitive called broadcast encryption, it is possible to securely distribute content by simply creating a ciphertext, which is compact regardless of the number of recipients. Our research team is working on the design of more flexible, secure, and efficient functional encryption and broadcast encryption.

Design and Evaluation of More Secure Cryptography

Practical cryptography must achieve a high level of security, one which remains secure even with the best information processing technology available today. In recent years, cryptography is also required to be secure against quantum computers, which are expected to be put to practical use in the future. We are developing cryptographic techniques that are secure now and would remain secure in the future. We are also conducting research to analyze the security of a wide range of cryptographic techniques, including those used in practice today and those currently under research.

Privacy-Preserving Information Analysis

Cloud computing, big-data analyses, and networked household electrical appliances demand technology to securely and efficiently analyze private information. Our research team studies technology to protect and analyze information. Our research topics include private database search, which allows us to search a database while keeping queries and database contents private.