Steganalysis of Semi-fragile Watermarking Systems Resistant to JPEG Compression

Recently, dozens of semi-fragile digital watermarking systems have been designed to protect JPEG images from unauthorized changes. Their principle is to embed an invisible protective watermark into the image. Such a watermark is destroyed by any image editing operations, except for JPEG compression with the quality level in a given range of values. Watermarking systems of this type have been assessed in terms of watermark extraction accuracy and visual quality of the protected image. However, their steganographic security (i.e., robustness against detecting protective information traces by a third party) has not been sufficiently studied. Meanwhile, if an attacker detects the presence of a watermark in the image, he can get valuable information on the used image protection technique. It can let him develop a data modification method that alters the content of the protected image without destroying the embedded watermark. In this paper, we propose a specific attack to analyze steganographic security of known semi-fragile watermarking algorithms for JPEG images. We also investigate the efficiency of the proposed attack. In addition, we propose an approach to counter the attack that can be applied in the existing watermarking systems to enforce their steganographic security.