In this paper, a technique of image watermarking using multiple images as watermarks is presented. The technique is based on transform domain functions including discrete wavelet transform (DWT), discrete cosine transform (DCT) and singular value decomposition (SVD) with an image as the host signal i.e. the watermarks will be used as proofs of the authenticity of the host image. The technique is executed by performing multilevel DWT followed by applying DCT and SVD to both the host and watermark. Multiple watermarks are used for the insurance of better security level. The scheme is immune to common image processing operations & some attacks and exhibits PSNR of 108.3781dB, normalized cross correlation (NCC) over 0.99 and normalized correlation (NC) over 0.99.Image watermarking is defined as the process of embedding information in an image which will act as the host image. The embedded information can be any type of media like audio, text or another image. The embedded information should be protected and extracted which will be used for copyright protection and the verification of the host image. Digital image watermarking can be of two types: visible and invisible. The requirements of invisible watermarking are imperceptibility. On the other hand, in the case of visible watermarking, the watermark should be visible so that the hidden data can be easily detected [2]. Due to the rapid increase of sharing of data through the internet because of the higher speed of information transmission and reception, Preprints (www.preprints.org) | NOT PEER-REVIEWED | it has become very important to protect the authenticity of a signal being sent. It is also very important to provide security to multimedia as well as to protect it from various forms of forgery in an efficient manner with respect to the speed of verification process [3]. Image watermarking can be done on the spatial domain as well as on the transform domain. Several functions were used to implement the transform domain watermarking i.e. the watermarking algorithm can be developed by using transform domain functions such as discrete cosine transform(DCT) [4][5], discrete wavelet transform (DWT) [6][7], singular value decomposition (SVD) [8-10], fast Fourier transform (FFT), contour-let transform (CT), and Wigner transform (WT),etc. Before watermarking, some modifications can be done on the host image to increase the efficiency of watermarking [11]. A modification can be also done on the watermark which is proved to be a very powerful factor for better performance [12]. The combination of different transform domain functions is used to develop very powerful watermarking algorithm [13][14]. Further, the use of multiple watermarks can add an extra dimension to the achievement of privacy and authenticity [15][16]. Another method of multiple-watermarking is inserting the same information several times into the host image. This method is very fruitful in increasing the visual and statistical invisibility of hidden information [17].
Image Watermarking with Image as the...
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