Secure Asymmetric Watermark Detection Without Secret of Modified Pixels. - Mitsuo Okada; Hiroaki Kikuchi (WISA, 2005)

Multi-Bit Embedding in Asymmetric Digital Watermarking without Exposing Secret Information. - Mitsuo Okada; Hiroaki Kikuchi; Yasuo Okabe (IEICE Trans. Inf. Syst., 2008)

Semi-blind Fingerprinting Utilizing Ordinary Existing Watermarking Techniques. - Mitsuo Okada; Yasuo Okabe; Tetsutaro Uehara (IWDW, 2009)

Security Analysis on Privacy-Secure Image Trading Framework Using Blind Watermarking. - Mitsuo Okada; Yasuo Okabe; Tetsutaro Uehara (SAINT, 2009)

A Web-Based Privacy-Secure Content Trading System for Small Content Providers Using Semi-Blind Digital Watermarking. - Mitsuo Okada; Yasuo Okabe; Tetsutaro Uehara (CCNC, 2010)

User-friendly digital watermark extraction using semi-transparent image. - Mitsuo Okada; Sakito Matsuyama; Yoshinori Hara (CCNC, 2011)

New CAPTCHA for smartphones and tablet PC. - Mitsuo Okada; Sakito Matsuyama (CCNC, 2012)