Cryptography Using Contrast Enhancement

Abstract

The proposed method of cryptography using contrast enhancement consists of two processes - extraction and recovery. Very often, the communication is required to be secure when the data is sensitive. The existing methods such as the Difference Expansion and Expansion Embedding suffer from undesirable distortion, which makes these methods unsuitable or less reliable. These methods use FFT (fast fourier transform) and this may result in loosing the data at the receiver part. The technique used in proposed system is discrete wavelet transform to achieve data without any loss. The message is embedded into cover image based on key and then, the covered image is transmitted. In this proposed system, one first contribution is a histogram shifting modulation, which adaptively takes care of the image content using the image prediction-errors and, by considering their immediate neighbourhood, the proposed scheme inserts data in textured areas where other methods fail to do so. This method inserts the carrier (cover) in the textured area and thus reduces the distortion. It also increases the embedding capacity of the cover image. In that way, the message embedded and extractor remain synchronized for message extraction and image reconstruction.