Bounded Gaussian fingerprints and the gradient collusion attack [multimedia fingerprinting applications]

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 three large classes of spread-spectrum fingerprints using a recently introduced collusion procedure, the gradient attack. Surprisingly, we show that the collusion resistance of direct-sequence and uniformly distributed spread spectrum fingerprints is a small constant that does not depend on the object size, whereas bounded Gaussian fingerprints demonstrate significantly better robustness to the gradient attack.