Coverless Information Hiding Based on Robust Image Hashing

Traditional image steganography modifies the content of the image more or less, it is hard to resist the detection of image steganalysis tools. New kind of steganography methods, coverless steganography methods, attract research attention recently due to its virtue of do not modify the content of the stego image at all. In this paper, we propose a new coverless steganography method based on robust image hashing. Firstly, we design an effective and stable image hash by using the orientation information of the SIFT feature points. Then the local image database is created and the corresponding hash values of these images in the database are computed. Secondly, the secret message is divided into segments with the same length as the hash sequences. And a series of images are chosen from the image database by matching the secret information segments and the hash sequences of all the images. Finally, these images are transmitted as the carriers of the secret information. When the receiver receives these images, the secret information is extracted by using the shared hash method. Due to the characteristics that SIFT features can resist common image attacks in a certain extent, the secret information corresponding to the hash has strong robustness. To improve the retrieval and matching efficiency of the hashing system, an inverted index of quadtree structure is designed. Compared with the traditional image steganography, this method does not modify the content of the image itself, therefore, can effectively resist steganalysis tools. Furthermore, we compare the proposed method with state-of-art coverless steganography method which also based on image hash, and experimental results show that our method has higher capacity, robustness and security than the method proposed in [15].