Steganalysis of YASS

In this paper, we describe a method for attacking Yet Another Steganographic Scheme (YASS), which is designed to be a very secure JPEG steganographic algorithm. The success of YASS is attributed to its innovation in embedding, i.e., hiding data in embedding host blocks whose locations are randomized. However, we find that the locations of the embedding host blocks are not randomized enough. Some locations in an image are possible to hold an entire embedding host block and some locations are definitely not. Additionally, YASS employs a Quantization Index Modulation (QIM) embedding strategy in order to enhance the robustness of the embedded data, which on the other hand introduces extra zero coefficients into the embedding host blocks during data hiding. Consequently, statistical features extracted from locations which are possible to hold embedding host blocks are different from those from locations which are impossible to hold embedding host blocks. The trace of YASS embedding is therefore exposed.