Anti-forensics of contrast enhancement in digital images

Abstract

The blind detection of contrast enhancement in digital images has attracted much attention of the forensic analyzers. In this paper, we propose new variants of contrast enhancement operators which are undetectable by the existing contrast enhancement detectors based on the peak-gap artifacts of the pixel graylevel histogram. Local random dithering is introduced into the design of contrast enhancement mapping for removing such artifacts. Effectiveness of the proposed anti-forensic scheme is validated by experimental results on a large image database for various parameter settings. Both detectability and the resulting image quality are evaluated via comparison with the traditional contrast enhancement. The developed anti-forensic techniques could verify the reliability of existing contrast enhancement forensic tools against sophisticated attackers and serve as the targets for developing more reliable and secure forensic techniques.