DCT Based Digital Image Watermarking System

Abstract

Digital image watermarking is a method trying to embed small image inside a large original image. The original image will be converted into frequency domain to obtain the Discrete Cosine Transform (DCT) matrices from its block. DCT is mathematical tools, for embedding data into an image, to transform a signal from spatial to frequency domain. The logo image is embedded in random color components of the original image, as well as in random positions in each selected block. RC4, a pseudorandom bit generator, produces a stream of 8-bit numbers that are supposed to be truly random. The stream cannot be predicted without knowledge of the input key. RC4 is used to prevent from attackers when transferring watermark digital image pass over insecure network. After constructed the digital watermark image, send the image from sender side to receiver side. On the receiver side, accept the watermark image and extract the watermark image, by using IDCT and hidden logo image is received at the receiver side.