Publication

Abstract : In this paper we propose a DWT based dual watermarking technique wherein both blind and non-blindnbsp;algorithms are used for the copyright protection of the cover/host image and the watermark respectively.nbsp;We use the concept of embedding two watermarks into the cover image by actually embedding only one, tonbsp;authenticate the source image and protect the watermark simultaneously. Here the DWT coefficients of thenbsp;primary watermark (logo) are modified using another smaller secondary binary image (sign) and the midfrequencynbsp;coefficients of the cover/host image. Since the watermark has some features of host imagenbsp;embedded in it, the security is increased two-fold and it also protects the watermark from any misuse ornbsp;copy attack. For this purpose a new pseudorandom generator based on the mathematical constant p hasnbsp;been developed and used successfully in various stages of the algorithm. We have also proposed a newnbsp;approach of applying pseudo-randomness in selecting the watermark pixel values for embedding in thenbsp;cover image. In all the existing techniques the randomness is incorporated in selecting the location tonbsp;embed the watermark. This makes the embedding process more unpredictable. The cover image which isnbsp;watermarked with the signed-logo is subjected to various attacks like cropping, rotation, JPEGnbsp;compression, scaling and noising. From the results it has been found that it is very robust and has goodnbsp;invisibility as well.