An Improved Watermarking Technique for Image Authentication.

Abstract

Digital Watermarking is a technique which embeds a watermark signal into the host image in order to authenticate it. In our previous work [1], a binary watermark pattern was constructed from the information content of the image by selecting the minimum value from every block of size 2x2, and was disordered with the help of Arnold Transform but which was not showing a fine robustness against compression and rotation operation. As a solution to this issue, an innovative watermarking scheme is proposed. According to this, the low frequency subband of wavelet domain and the rescaled version of original image are utilized in the watermark construction process. A scrambled version of watermark is obtained with the help of Arnold Transform. The operation of embedding and extraction of watermark is done in high frequency domain of Discrete Wavelet Transform since small modifications in this domain are not perceived by human eyes. This watermarking scheme deals with the extraction of the watermark information in the absence of original image, hence the blind scheme was obtained. Peak Signal to Noise Ratio (PSNR) and Similarity Ratio (SR) are computed to measure image quality. In addition, the competency of the proposed method is verified under common image processing operations and a comparative study is made against the previous technique. Keywords