Collusion of fingerprints via the gradient attack

The difficulty of building an effective digital rights management system stems from the fact that traditional cryptographic primitives such as encryption or scrambling do not protect audio or video signals once they are played in plain-text. This fact, commonly referred to as "the analog hole," has been responsible for the popularity of multimedia file sharing which cannot be controlled, at least technically, by content's copyright owners. In this paper, we explore a specific issue in multimedia fingerprinting as an answer to "the analog hole" problem. We analyze the collusion resistance of spread-spectrum fingerprints with an arbitrary probability distribution of their source using a recently introduced collusion procedure, the gradient attack.