A Comparative Analysis on Various Strategies of Image Compression In Steganography |
Steganographic techniques can be used to hide data withindigital images with little or no visible change in the perceived appearance ofthe image and can be exploited to export sensitive information. Since imagesare frequently compressed for storage or transmission, effective steganographymust employ coding techniques to counter the errors caused by lossy compressionalgorithms. The Joint Photographic Expert Group (JPEG) compression algorithm,while producing only a small amount of visual distortion, introduces arelatively large number of errors in the bitmap data. It is shown that, despiteerrors caused by compression, information can be steganographically encodedinto pixel data so that it is recoverable after JPEG processing, though notwith perfect accuracy. We demonstrate that one can adapt recent diffusion-basedimage compression techniques such that they become ideally suited forSteganographic applications. Thus, the goal is to embed secret images withinarbitrary cover images. We hide only a small number of characteristic points ofthe secret in the cover image, while the remainder is reconstructed withedge-enhancing anisotropic diffusion in painting. Even when using significantlyless than 1% of all pixels as characteristic points, sophisticated shapes ofthe secret can be clearly identified. Selecting more characteristic point’sresults in improved image quality. In contrast to most existing approaches,this even allows to embed large colour images into small grayscale images. Steganography is the art of hiding the fact thatcommunication is taking place, by hiding information in other information. Manydifferent carrier file formats can be used, but digital images are the mostpopular because of their frequency on the Internet. For hiding secretinformation in images, there exists a large variety of Steganographictechniques some are more complex than others and all of them have respectivestrong and weak points. Different applications have different requirements ofthe steganography technique used.