Anti-forensics of JPEG Detectors via Adaptive Quantization Table Replacement

Due to the popularity of JPEG compression standard, JPEG images have been widely used in various applications. Nowadays, detection of JPEG forgeries becomes an important issue in digital image forensics, and lots of related works have been reported. However, most existing works mainly rely on a pre-trained classifier according to the quantization table shown in the file header of the suspicious JPEG image, and they assume that such a table is authentic. This assumption leaves a potential flaw for those wise forgers to confuse or even invalidate the current JPEG forensic detectors. Based on our analysis and experiments, we found that the generalization ability of most current JPEG forensic detectors is not very good. If the quantization table changes, their performances would decrease significantly. Based on this observation, we propose a universal anti-forensic scheme via replacing the quantization table adaptively. The extensive experimental results evaluated on 10,000 natural images have shown the effectiveness of the proposed scheme for confusing four typical JPEG forensic works.