In this paper, we investigate how existing theoretical contributions on usable security can serve to guide the design of a specific system. We illustrate how going through this theoretically informed, concrete design process, also provides the basis for complementing existing theoretical contributions. The system we have designed is a system taking advantage of pervasive computing technology to offer hotel guests access to their personal, digital materials while in a hotel room. The design is based on two ideas novel to usable security, namely falsification and the singleton invariant..