Source Camera Identification for Low Resolution Heavily Compressed Images

In this paper, we propose a method to exploit photo response non-uniformity (PRNU) to identify the source camera of heavily JPEG compressed digital photographs of resolution 640 times 480 pixels. Similarly to research reported previously, we extract the PRNU patterns from both reference and questioned images using a two-dimensional high-pass filter and compare these patterns by calculating the correlation coefficient between them. To deal with the low quality compressed image material, we propose a simple and effective way to obtain the PRNU. We did extensive experiments for both the closed and open set source camera identification problem with a set of 38 cameras of four different types. For the closed set problem accuracies as high as 83% for single images and 100% for around 20 simultaneously identified questioned images were obtained. For the open set problem, decision levels were obtained for several numbers of simultaneously identified questioned images. The corresponding false rejection rates were unsatisfactory for single images, but improved substantially for simultaneous identification of multiple questioned images.