Abstract
This paper proposes hybrid data representation schemes to improve the performance of a DCT-based steganographic method called StegErmelc1). Even though StegErmelc simultaneously achieves scalable carrier capacity, high embedding efficiency, and low SDR (stego detectable rate), SDR of StegErmelc increases sharply when the embedding rate is increased to more than 0.10bpc. SDR of StegErmelc also varies significantly when using different parameters. To suppress the sharp increase of SDR and to reduce the performance gap when using different parameters, we propose a new algorithm that keeps as many blocks that are operating in block mode as possible, and changes their encoding modes, one at a time, to gradually and accurately increase their carrier capacities. Experimental results show that, when embedding the same amount of information, the proposed method achieves lower SDR than that of StegErmelc and the performance gap of the proposed method is also found to be smaller than that of StegErmelc. The proposed method stays undetectable when embedding up to 0.125bpc. Basic performance of StegErmelc is also confirmed to be consistent regardless of the image database in use.
