A LWT and DCT based Blind Watermarking Scheme for Digital Images

Abstract

As a potential solution to defend unauthorized replication of digital multimedia objects, digital watermarking technology is now attracting significant attention. With a combination of Lifting Wavelet Transform (LWT) and Discrete Cosine Transform (DCT), the system is presented. Key sequences used for watermark embedding and extraction are generated by Linear Congruential Generator (LCG). Moreover, for the sake of security enhancement, double coded image puzzling method is created. The LWT is applied to decompose the original image into four sub-band images. Then the DCT is computed on the selected sub-band of the LWT coefficients. The watermark bits are modified by LCG and embedded in the DCT transformed of the selected LWT sub-band of the original image. The Doublecoded image puzzling is created in order not to recognize the meaningful image by illegal users. The proposed system mainly focuses on an invisible watermark embedding, imperceptibility of watermarked image, blind watermarking by using key sequence instead of using original image, and robustness for watermark extraction. The presented system is realized in MATLAB.