Anti-forensics of JPEG compression

Abstract

The widespread availability of photo editing software has made it easy to create visually convincing digital image forgeries. To address this problem, there has been much recent work in the eld of digital image forensics. There has been little work, however, in the eld of anti-forensics, which seeks to develop a set of techniques designed to fool current forensic methodologies. In this work, we present a technique for disguising an image's JPEG compression history. An image's JPEG compression history can be used to provide evidence of image manipulation, supply information about the camera used to generate an image, and identify forged regions within an image. We show how the proper addition of noise to an image's discrete cosine transform coef cients can suf ciently remove quantization artifacts which act as indicators of JPEG compression while introducing an acceptable level of distortion. Simulation results are provided to verify the ef cacy of this antiforensic technique.

Digital image forensics: a booklet for beginners

“…For this reason, technique [87] cleans blocking artifacts by applying first a median filter and then adding low-power white noise to the image. It is shown that this operation outperforms existing de-blocking techniques when coupled to method [86] for compression hiding. "Polished" images are then recompressed with quantization tables typical of other cameras, and their quantization matrices estimated through method [70].…”

“…A different method for counterfeiting image source fingerprints is proposed in [87], and is based on the manipulation of JPEG artifacts. The authors present a technique complimentary to [86] for the suppression of traces of compression and then re-forge the image by compressing it with a different quantization table, e.g. characteristic of another device.…”

“…characteristic of another device. While method [86] restores a plausible histogram for unquantized images, it does not eliminate visual compression artifacts, i.e. blockiness.…”

“…An investigator retrieving convincing CFA artifacts in contrast with other tampering traces might eventually assume it as further proof of manipulation. Stamm and others in [86] attempt at covering traces of previous compressions by modifying the distribution of the DCT coefficients before saving the tampering results. After compression, DCT coefficients are clustered around the integer multiples of the quantization step, as discussed in section 4.2.3.…”

Forensics, Anti-forensics and Counter Anti-forensics for JPEG Compressed Images

“…The first attempts to make JPEG footprints forensically undetectable on the basis of DCT artifacts are the techniques introduced by stamm et al in their papers in [17,18]. In the first paper, quantisation gaps in the DCT histogram are reduced by spreading the coefficients with an additive noise called anti-forensic dither.…”