Collaboration among organizations or individuals is common. While these participants are often unwilling to share all their information with each other, some information sharing is unavoidable when achieving a common goal. The need to share information and the desire to keep it private are two competing notions which affect the outcome of a collaboration. This paper proposes a formal model of collaboration which addresses privacy concerns. We draw on the notion of a plan which originates in the AI literature. We consider transition systems in which actions have pre- and post-conditions of the same size. We show it is PSPACE-complete to decide whether a given such system protects the privacy of its participants and whether it contains a plan leading from a given initial state to a desired goal state. This is joint work with Max Kanovich and Andre Scedrov.