Robust and Secure Multiple Watermarking in Wavelet Domain

This paper presents a secure multiple watermarking scheme in which the image along with the encrypted and encoded text acts as a watermarks. The algorithm is based on discrete wavelet transform (DWT) and singular value decomposition (SVD) for embedding. In the embedding process, the cover medical image is decomposed up to second level of DWT coefficients. The image and text watermark is embedded into of the first and second level DWT respectively. In order to enhance the robustness and security of the text watermark, encryption and error correcting code (ECC) is applied to the ASCII representation of the text watermark before embedding. Results are obtained by varying the gain factor, size of watermark, and medical image modalities. Experimental results are provided to illustrate that the proposed method is able to withstand a variety of signal processing attacks. The method is compared with other reported techniques and has been found to be giving superior performance for robustness and imperceptibility suggested by other authors. Furthermore, robustness of the proposed method is tested by using the benchmark software Checkmark and is found to be robust against numerous known attacks such as JPEG, JPEG2000 compressions, cropping, Gaussian etc.