Content-independent steganography and steganalysis of JPEG images

This paper studies the possibilities of hiding data within a JPEG file without making any changes to the image content, and in a way that any JPEG decoder normally opens the file. These possibilities are found by careful studying the JPEG file format. A steganalysis system needs to check these simple embedding techniques before complicated analyses of DCT coefficients. We also present a number of system attacks on JPEG files, which can lead to detection of hidden data. The attacks are based on the fingerprints left in the stego file by JPEG encoders, or the steganography algorithm itself.