An adaptive DCT-based Mod-4 steganographic method

This paper presents a novel Mod-4 steganographic method in discrete cosine transform (DCT) domain. A group of 2 × 2 quantized DCT coefficients (GQC) is selected as the valid embedding area if more than two DCT coefficients are outside the interval of [-1,1]. The modulo 4 arithmetic operation is further applied to all the valid GQCs to embed a pair of binary bits using the shortest-route modification scheme. Each secret message is also encrypted to provide the system with more security. The proposed system has been extensively tested on a variety of images with different textures. Experimental results demonstrate that our system successfully preserves the quality of the images and stays undetected by the well-known steganalysis methods.