Forensic characterization of image capture devices

Khanna, Nitin Ph.D., Purdue University, December, 2009. Forensic Characterization of Image Capture Devices. Major Professor: Edward J. Delp. Forensic characterization of sensors or devices is important in many applications such as establishing the trust and verifying authenticity of data produced by a sensor or device and the sensor or device that created it. Recently there has been a great deal of interest using features intrinsic to a data-generating sensor for the purpose of source identification. Numerous methods have been proposed for various problems related to sensor forensics in general and image forensics in particular. Although a considerable amount of work has been done in forensic identification of digital cameras, more work needs to be done in forensic characterization of scanners, video cameras and other audio devices. This thesis is aimed at developing tools for forensic characterization of devices or sensors, in particular image capture devices. Statistical feature based classifiers are designed for imaging sensor classification and for source scanner identification for images acquired using flatbed desktop scanners. The methods are based on us­ ing imaging sensor pattern noise for scanned photographs and texture features for scanned documents, as device fingerprints. The statistical feature vector based meth­ ods provide high accuracies, both for native resolution and lower resolution scanned images. The proposed method perform well with images that have undergone JPEG compression with low quality factors, image sharpening, and contrast stretching. The proposed features are also robust to the scan area used for a particular scan so knowl­ edge of the exact location of scanner’s bed used for scanning is not needed. The sensor noise based source scanner identification scheme is extended for forgery detection in scanned photographs scanned at native resolution of the scanners. This