Introduction to Fusion–Based Digital Visual Media Forensics
Digital Visual Media Forensics (DVMF) is a branch of digital forensics that deals with the recovery and repair, scientific examination and investigation, comparison, and in–depth evaluation and interpretation of digital visual evidence, so as to ascertain its integrity and legitimacy, in mostly (civil or criminal) legal matters. DVMF is a multifaceted discipline, and among all the operations it entails, detection of conscious semantic manipulations (i.e., tamperings or forgeries) is perhaps the most explored; over two decades of research in this field has resulted in a considerable body of tools and techniques aimed at detecting the signs of all potential visual manipulations that can affect the integrity of a digital image or video.
All such tamper detection techniques are highly specialized, i.e., each of them is designed to detect traces of a specific kind of manipulation. In a real–world heterogeneous forensic scenario, however, the analyst is largely unaware of the processing history of the given content, which means that the application of a single technique is largely insufficient for the authentication of the given content. The most viable course of action in such a case is to use multiple tamper detection techniques, each of which specializes in the exposition of a particular kind of forgery, and then combine the evidence provided by all these techniques to reach a final decision regarding the authenticity of this content.
While this process of combining evidence generated from multiple forensic techniques seems simple enough in theory, in reality, this task is much more complicated, especially considering the fact that existing forensic techniques are mired in uncertainties and sometimes proffer incomplete, ambiguous, or even conflicting evidence regarding the presence (or absence) of a particular forensic artifact in the given content. Accurate and definitive decision–making in such situations, therefore, becomes contingent on how effectively we handle such uncertainties and ambiguities, a challenge that is accomplished with the help of a special branch of DVMF, which we will refer to as Fusion–Based Forensics.
The primary aim of this course is to familiarize the participants with all aspects of the domain of fusion–based forensics. We will begin with a detailed discussion of the basic concepts of uncertainty and ambiguity, followed by an analysis of the various factors that cause uncertainties and ambiguities in the domain of digital visual media forensics. This discussion will be followed by an overview of the fundamental aspects of the various theories and strategies that provide means for combining uncertain, conflicting, or incomplete pieces of evidence, and examine how these theories and strategies are employed in the domain of tamper detection and evidence authentication.