P. Sénac, M. Ott, and A. Seneviratne (Eds.): ICWCA 2011, LNICST 72, pp. 433–444, 2012. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2012 3D-DCT Based Zero-Watermarking for Medical Volume Data Robust to Geometrical Attacks Jingbing Li 1 , Wencai Du 1 , Yong Bai 1 , and Yen-wei Chen 2 1 College of Information Science and Technology, Hainan University, Haikou 570228, China 2 College of Information Science and Engineering, Ritsumeikan University, Kasatsu-shi 525-8577, Japan Jingbingli2008@hotmail.com, wencai@hainu.edu.cn, bai@hainu.edu.cn, chen@is.ritsumei.ac.jp Abstract. This paper presents a method for robust watermarking of medical volume data using 3D-DCT. A feature vector of the volume data is utilized to enhance the robustness against rotation, scaling, translation, and cropping changes. The proposed algorithm utilizes the volume data’s feature, Hash function, the third party authentication. We describe how to obtain the feature vector of medical volume data and embed and extract the watermarking. Simulation results demonstrate the proposed algorithm’s robustness against rotation up to 30°, against scaling down to 20% of the image's original size, and against translation transform up to 10%. Keywords: 3D-DCT, Digital watermarking, Medical volume data, Robust, Geometrical attacks. 1 Introduction With the advancing of the multimedia and internet technology, telediagnosis, telesurgery and cooperative working session have been undergoing rapid development. However, when Electronic Patient Records(EPR) and medical images are transmitted on the Internet, there may be the risk of disclosure of personal privacy[1][2]. Medical image watermarking can be a effective technology to solve this problem[3][4]. Traditionally Digital watermarking technology is used in the copyright protection of digital media first. Using watermark's properties of invisibility and robustness, patient information, doctor diagnosis and Electronic Patient Records can be used as the watermarking hidden in the CT, MRI (Magnetic Resonance Imaging) and other medical images[5]. Medical image watermarking is usually divided into three types [4]. 1) RONI(Region of non-interest)-based medical image watermarking. The content of medical images can not tolerate significant changes when watermarking is embedded. Hence, the watermarking information is embedded in the RONI of the medical images[6][7]. However, the capacity of hidden information is limited because most of the RONI area of the image is the black background.