A general framework for robust watermarking security

The analysis of the security of watermarking algorithms has received increasing attention since it has been recognized that the sole investigation of robustness issues is not enough to properly address the challenges set by practical applications. Such a security analysis, though, is still in its infancy, up to a point that a general agreement has not yet been reached even on the most fundamental problems. The purpose of this paper is to provide a general security framework encompassing most of the problems encountered in real-world applications. By considering the amount of information the attacker has about the watermarking algorithm, we introduce the notion of fair and un-fair attacks, so to ease the classification of different systems and attacks. Though we recognize that many important differences exist between watermarking and cryptographic security, a large part of our work is inspired by the Diffie-Helmann's paradigm, which is widely used in cryptography. For each class of systems great care is taken to describe both the attacker's and watermarker's point of view, presenting the challenges raised by each system to these different actors. Finally, we try to outline some research directions which, according to us, deserve further analysis.