Steganalysis on JPEG Decompressed Bitmaps Revisited

It´s well known that the spatial ±1 steganography on JPEG decompressed images is relatively easier to detect than those never compressed ones. Though some targeted methods that are special for JPEG decompressed carriers are designed, there are still some drawbacks among them. First, most methods are not perfect or even don´t work for embedding rate as low as 0.0003 bits per pixel, or even lower. Second, few methods are able to estimate embedding rate for LSB matching. Finally, many methods require estimation of the JPEG quality factor, which makes the methods slow and not so robust for big JPEG quality factors. This paper revisited a color based method raised by Westfeld ten years ago, unearthed the reason why it´s so reliable and also extended it to a practical non-parameter quantitative steganalyzer for JPEG decompressed carriers. Error rates of our new method was evaluated in this paper.