Share with strangers: Privacy bubbles as user-centered privacy control for mobile content sharing applications

A continually increasing number of pictures and videos is shared in online social networks. Current sharing platforms, however, only offer limited options to define who has access to the content. Users may either share it with individuals or groups from their social graph, or make it available to the general public. Sharing content with users to which no social ties exist, even if they were physically close to the places where content was created and witnessed the same event, is however not supported by most existing platforms. We thus propose a novel approach to share content with such users based on so-called privacy bubbles. Privacy bubbles metaphorically represent the private sphere of the users and automatically confine the access to the content generated by the bubble creator to people within the bubble. Bubbles extend in both time and space, centered around the collection time and place, and their size can be adapted to the user's preferences. We confirm the user acceptance of our concept through a questionnaire-based study with 175 participants, and a prototype implementation shows the technical feasibility of our scheme.