Realizing privacy by definition in social networks

Privacy violations in online social networks (OSNs) have become more the norm than the exception. Conventional models of privacy in OSNs offer a limited set of privacy guarantees for information posted and reshared by users in OSNs. In this paper, we propose a completely new model of private information sharing using a refined abstraction of contexts that embodies the philosophy of contextual integrity (CI), which we believe better captures users privacy expectations in OSNs. We present the design of Compass, an online social network inspired by CI, in which three properties hold: (a) users are associated with roles in specific contexts; (b) every piece of information posted by a user is associated with a specific context; (c) norms defined on roles and attributes of posts in a context govern how information is shared across users within that context.