Resilience of digital watermarks under transformation attacks

Abstract

Digital watermarking of electronic data has become a popular research area over last several years. The research work presented in this thesis blends a more practical perspective of digital watermarking schemes against transformation/geometric attacks with theoretical studies presented in past literature. Main objective of this dissertation is to come up with an attack success/failure evaluation metric against chosen watermarking schemes and with set of attacks. \Success" or \Failure" is defined as per given criteria: If there is a legitimate owner for the image, success of image attack would be determined if recovery of the watermark is denied given the fact that attacked image lies within the perceptual range. Otherwise it would be depicted as a failure of image attack. In this thesis, limits that preserve perceptual quality of subjected images were analyzed for different types of attacks. Both PSNR and Histogram Analysis provide a foundation for meaningful measurement. We have shown that coupling such measurements with a perceptual quality measurement provide meaningful values for effectiveness of a watermarking scheme.