On covert collaboration

In the conventional steganographic framework, a covert message is hidden within a larger, seemingly innocent message. We argue that this framework must be extended in order to adequately model the means and goals of modern collaborative systems. Whereas messages are static objects with a single creator, collaborative systems are dynamically changed by multiple entities according to rules and patterns specific to the given system. The primary contribution of this paper is to frame the general question: When can one steganographically embed collaborative system A into collaborative system B? As a case study, we develop a system for embedding a simple wiki into the Flickr photo sharing service. We develop techniques for steganographically embedding a collaborative system whose update rules are quite different than those of the host service.