An approach to expose dithering-based JPEG anti-forensics

A forensic analyst needs to exploit various kinds of artefacts for developing a powerful forensic technique. Among those, the JPEG compression artefacts such as blocking artefacts & DCT histogram artefacts are the most widely used. JPEG anti-forensic techniques aim to disguise forensic detectors by removing these artefacts. Hence, a technique for the detection of dithering-based JPEG anti-forensic methods is the need of an hour. An approach proposed in this paper exploits the spread of discrete cosine transform (DCT) coefficients around integer multiple of quantization step size with repeated application of dithering-based JPEG anti-forensics. The paper first briefly explains dithering-based state-of-the-art JPEG anti-forensic techniques. Then the proposed method is illustrated thoroughly, and finally, experimental results are reported to demonstrate the accuracy of the proposed method.