Camera identification from printed images

In this paper, we study the problem of identifying digital camera sensor from a printed picture. The sensor is identified by proving the presence of its Photo-Response Non-Uniformity (PRNU) in the scanned picture using camera ID methods robust to cropping and scaling. Two kinds of prints are studied. The first are postcard size (4" by 6") pictures obtained from common commercial printing labs. These prints are always cropped to some degree. In the proposed identification, a brute force search for the scaling ratio is deployed while the position of cropping is deter-mined from the cross-correlation surface. Detection success mostly depends on the picture content and the quality of the PRNU estimate. Prints obtained using desktop printers form the second kind of pictures investigated in this paper. Their identification is complicated by complicated geometric distortion due to imperfections in paper feed. Removing this distortion is part of the identification procedure. From experiments, we determine the range of conditions under which reliable sensor identification is possible. The most influential factors in identifying the sensor from a printed picture are the accuracy of angular alignment when scanning, printing quality, paper quality, and size of the printed picture.