Discrete Wavelet Transform Based Strongly Robust Watermarking Scheme for Information Hiding in Digital Images

The performance evaluation of watermarking scheme is done by two performance metrics: perceptual transparency and robustness. Perceptual transparency refers quality of image which is measured by ‘Peak Signal to Noise Ratio’ (PSNR). Robustness is measured in terms of ‘Correlation Factor’ (ρ). A good quality watermarking scheme should have maximum PSNR, ideally Correlation Factor equals to 1 and should have maximum watermark information hiding capacity. In this paper, we have presented strongly robust digital image watermarking scheme based on ‘Discrete Wavelet Transform’, by embedding scrambled watermark in middle frequency sub band. The security levels are increased by generating PN sequence depending on periodicity of watermark image. The image scrambling is applied by Arnold Transform. The decomposition is done with ‘Haar’ which is simple, symmetric and orthogonal wavelet and the direct weighting factor is used in watermark embedding and extraction process. The scheme results in exact recovery of watermark with standard database images of size 512x512, giving Correlation Factor equals to 1. The Correlation Factor for different attacks like Noise addition, Filtering, Rotation and Compression ranges from 0.90 to 0.95. The PSNR with weighting factor 0.02 is up to 48.53 dBs. The presented scheme is nonblind and embeds binary watermark of 64x64 size.