A Speech Scrambler Using the Fast Fourier Transform Technique. - Keiichi Sakurai; Keiichiro Koga; Takuro Muratani (IEEE J. Sel. Areas Commun., 1984)

An analog speech scrambling system using the FFT technique with high-level security. - Akira Matsunaga; Keiichiro Koga; Michihisa Ohkawa (IEEE J. Sel. Areas Commun., 1989)

A simple decoding of BCH codes over GF(2m). - Keiichiro Koga (IEEE Trans. Commun., 1998)

Compactification of Low-Cost Servo Valve Using Buckled Tubes and Its Application. - Shota Harada; Tetsuya Akagi; Shujiro Dohta; Wataru Kobayashi; Keiichiro Koga; Abdul Nasir Bin Abd (ICMSSP, 2016)