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In this paper pixel value differencing based image authentication/data hiding technique through steganographic approach in spatial domain, termed as DHPVD, has been proposed. The numbers of secret bits of the hidden image that are embedded in consecutive two pixels of the source image depend on the difference between the pixels. More number of secret bits are inserted to the edge areas than smooth areas. 2×2 non overlapping mask is chosen from the source image in row major order. This scheme takes the difference between the two consecutive pixels. The difference may fall into any one of four levels such as lower, middle1, middle2 and higher. Then depending upon the difference level variable numbers of secret bits are embedded using a hash function in the consecutive two pixels in the non overlapping 2×2 mask. In addition to embedding the contents of the hidden image, dimension of the hidden image has also been embedded. A bit handling is used to minimize the difference between the source and embedded pixels. Reverse process is followed during decoding. Various statistical parameters computed are compared with the existing side match based steganographic algorithm devised by Cheng-Huing Yang et al. [1] and Chin-Chen Chang et al.[2] which show that proposed DHPVD obtained better result in terms of PSNR and IF.

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