Advanced Digital Forensic and Steganalysis Methods

摘要

The author developed and advanced a new class of digital forensic techniques to verify origin and integrity of digital imagery based on systematic artifacts of imaging sensors called photo-response non-uniformity (PRNU), which is caused by slight variations in physical dimensions of pixels and inhomogeneity of silicon. PRNU thus forms a unique fingerprint that characterizes an imaging device, such as a camera, camcorder, or scanner. Both CCD and CMOS technologies exhibit this type of irregularity. The specific achievements include perfecting the methodology for estimating the fingerprint from images, extending to cases when the image under investigation is simultaneously cropped, scaled, and processed, extending the technology when the digital image is printed, developing technology capable of determining the camera model from the fingerprint, and a large scale validation on millions of images from 6900 cameras of 150 models. The techniques have dual purpose and are important for information validation in military intelligence gathering, law enforcement, and forensic investigation.