Conditions for effective detection and identification of primary quantisation of re-quantized JPEG images

Abstract

The choice of Quantisation Table in a JPEG image has previously been shown to be an effective discriminator of digital image cameras by manufacturer and model series. When a photograph is recompressed for transmission or storage, however, the image undergoes a secondary stage of quantization. It is possible, however, to identify primary quantisation artifacts in the image coefficients, provided that certain image and quantisation conditions are met. This paper explores the conditions under which primary quantisation coefficients can be identified, and hence can be used image source identification. Forensic applications include matching a small range of potential source cameras to an image.