MRI Watermarking Technique Using Chaotic Maps, NSCT and DCT

Abstract

In this paper, magnetic resonance imaging (MRI) watermarking technique using chaotic maps, nonsubsampled contourlet transform (NSCT) and discrete cosine transform (DCT) has been proposed. Here, three chaotic maps, namely logistic map, Arnold's cat map, tent map are applied in multiple ways of watermarking. The number of iterations and the initial values of parameters of these maps are used as confidential keys, which strengthen the security of proposed watermarking. Here, the pixel positions of MRI are shuffled following the chaotic sequence of logistic map. The watermark is scrambled by Arnold's Cat map and then it is further scrambled by applying 3×3 mask and X-OR operation of tent map. NSCT is used in this watermarking scheme, since this transform assures superior performance than other transforms. Besides, the approximation band of NSCT contains considerable visual information of an image. DCT is applied on this approximation band, because NSCT along with DCT makes watermarking technique more imperceptible and robust. So, the DCT coefficients of shuffled watermark are embedded into the DCT coefficients of approximation band of shuffled MRI in this scheme. Furthermore, the proposed scheme is tested on varieties of MRIs and their associated results reveal that this scheme has promising improvements in imperceptibility and robustness against noise and geometric attacks.