Locating steganographic payloads by combining weighed-stego residuals and maximum a posteriori probability cover estimator

For the least significant bit (LSB) repalcement steganography, an improved cover estimation method is proposed by combining the weighted-stego(WS) residuals and the maximum a posteriori probability (MAP) cover estimator. First, the WS residuals are used to perform preliminary payload location. Next, the preliminary location result is applied to the improved MAP cover estimation method as a priori information so that a more accurate cover estimation algorithm will be obtained. Finally, the residual is computed to derive the final payload location result. Previous experiments have proved that the proposed method can improve the accuracy of payload location for the LSB replacement for either the spatial domain BMP image or the JPEG decompression image. It has a good robustness for different embedding rates.