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AIST > RISEC > Members > Koji NUIDA @AIST > Research Topics

Research Topics

My main research topics are the followings:

Digital content protection

Digital fingerprint techniques based on collusion-secure codes

I have been studying on digital fingerprint technology, that enables digital content servers to embed user identification information into the contents (movies, musics, etc.) before distribution, and thus to detect the guilty user when illegally copied/redistributed contents are found. In particular, I am currently interested in such techniques based on collusion-secure codes, from the following points of view:
(See also: RCIS Research Topics Secure fingerprinting codes for digital watermarking)

Selected results

Pseudorandom number generators and physical random number generators

Analysis of pseudorandom number generators

Many information security schemes are implemented by using pseudorandom numbers instead of theoretically complete random numbers. Thus it is important for preventing vulnerability to choose appropriately the pseudorandom numbers we use. In my research, I am analyzing performances of existing pseudorandom number generators mainly by mathematical methods.

Selected results

Secure implementation of information security schemes by using pseudorandom number generators

Many information security schemes are implemented by using pseudorandom numbers instead of theoretically complete random numbers. Thus it is important for preventing vulnerability to choose appropriately the pseudorandom numbers we use. I am investigating methods of implementing theoretically secure (by use of true random numbers) information security schemes by using pseudorandom numbers, mainly from a viewpoint of security evaluation methods of such implemented systems.

Selected results

Bias reduction methods for physical random number generators

There have been proposed random number generation methods based on several physical phenomena that may achieve ideal accuracy in theory. However, in practice even such physical random number generators in general possess some biases due to implementation errors, that may lead some problems in sensitive applications such as cryptography. I am investigating mathematical post-processing methods to reduce the biases of physical random numbers.

Selected results

Quantum information theory

Algorithms for quantum computer

It is a common belief, and also a security base of most of the present cryptosystems, that certain mathematical problems (such as Integer Factoring) cannot be solved efficiently by any computer of current type. However, quantum computers, which are essentially new computers and are well investigated recently toward realization, will be able to solve some of such problems (including Integer Factoring) very efficiently; this means that many of present cryptosystems will turn into insecure once quantum computers are realized. Nowadays cryptosystems based on problems difficult even for quantum computers have been investigated in researches on cryptography.
My research has analyzed which problems will in fact be efficiently solvable by quantum computers. In particular, I have been trying to establish new algorithms for quantum computers, by using certain method different from preceding researches.

Selected results

Research on quantum information theory from axiomatic and operational viewpoints

For unconditionally secure quantum cryptography (quantum key distribution) that is expected as a new-generation cryptographic scheme, its security is assured by theory of quantum mechanics. Recently, many works have been done on axiomatic and operational approaches to quantum information theory. In my research, I am mainly working on preparation and development of mathematical foundation of such research activities.

Selected results

Applications of mathematics to information security

I have applied, or intended to apply, some advanced mathematics to several topics of information security, including the above-mentioned ones.


Last Modified: April 3, 2012
(c) Koji NUIDA 2009: All Rights Reserved
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E-mail: jpk.nuida@aist.go.