Digital watermarking for copyright protection of digital audio data and digital image data

ABSTRACT DIGITAL WATERMARKING FOR COPYRIGHT PROTECTION OF DIGITAL AUDIO DATA AND DIGITAL IMAGE DATA TOKUR, Yüksel M.Sc. in Electrical and Electronics Eng. Supervisor: Assist. Prof. Dr. Ergun ERÇELEBİ January 2004, 80 pages Personal computers with internet connections have made the distribution of multimedia data and applications much easier and faster. Electronic commerce applications and online services are rapidly being developed. The digital media such as image, audio, video, 3D objects, etc. can be duplicated unlimitedly without any quality loss and can also be easily distributed and tempered. Therefore, digital watermarking is a good way to protect them from the risk of illegal copying, reproduction and distribution in a network environment. Digital watermark is an insensible signal in which digital data is embedded directly for copyright protection and for checking if data have been corrupted. Embedded watermark carries a certain amount of information relating to the owner, distributor or receiver of digital data. When the ownership of digital work is question, the embedded information can be extracted to completely characterize the owner. In general, a digital watermark technique must satisfy the following two properties for copyright protection. First the embedded watermark does not distort visually the image and audibly the audio data. And it should be invisible for the image watermarking and inaudible for the audio watermarking. The second property is that the watermark is difficult for an attacker to remove. It should be robust to common signal processing and geometric distortions. IVIn this thesis, we have developed robust digital watermarking methods for digital image data. The digital image watermarking methods were implemented in frequency domain and wavelet domain. Robustness of proposed digital image watermarking was tested by applying different types of attacks such as noise addition, image compression, cropping and rotation. Global performance was evaluated by means of the peak signal to noise ratio (PSNR) and bit error ratio (BER). Numerical results comparing the performances of the proposed digital image watermarking methods with that of the spatial domain methods were given. The results showed good performances and the watermark was extracted from the watermarked image successfully. Also, digital audio watermarking implemented in frequency domain by using psychoacoustic model had been presented in this thesis. The results obtained by proposed watermarking were given and the results indicated that the watermark was inaudible. Key words: digital image watermarking, digital audio watermarking, Fast Fourier transform, discrete wavelet transform, Gaussian noise.