Online social networks (OSNs) have experienced tremendous growth in recent years and become a de facto portal for hundreds of millions of Internet users. These OSNs offer attractive means for digital social interactions and information sharing, but also raise a number of security and privacy issues. While OSNs allow users to restrict access to shared data, they currently do not provide any mechanism to enforce privacy concerns over data associated with multiple users. To this end, we propose an approach to enable the protection of shared data associated with multiple users in OSNs. We formulate an access control model to capture the essence of multiparty authorization requirements, along with a multiparty policy specification scheme and a policy enforcement mechanism. Besides, we present a logical representation of our access control model that allows us to leverage the features of existing logic solvers to perform various analysis tasks on our model. We also discuss a proof-of-concept prototype of our approach as part of an application in Facebook and provide usability study and system evaluation of our method.

Most of existing online social networks, such as Facebook and Twitter, are designed to bias towards information disclosure to a large audience. Google recently launched a new social network platform, Google+. By introducing the notion of `circles', Google+ enables users to selectively share data with specific groups within their personal network, rather than sharing with all of their social connections at once. Although Google+ can help mitigate the gap between the individuals' expectations and their actual privacy settings, it still only allows a single user to restrict access to her/his data but cannot provide any mechanism to enforce privacy concerns over data associated with multiple users. In this paper, we propose an approach to facilitate collaborative privacy management of shared data in Google+. We extend and formulate a multiparty access control model, named MPAC+, to capture the essence of collaborative authorization requirements in Google+, along with a multiparty policy specification scheme and a policy enforcement mechanism. We also discuss a proof-of-concept prototype of our approach and describe system evaluation and usability study of our prototype.

We have seen tremendous growth in online social networks (OSNs) in recent years. These OSNs not only offer attractive means for virtual social interactions and information sharing, but also raise a number of security and privacy issues. Although OSNs allow a single user to govern access to her/his data, they currently do not provide any mechanism to enforce privacy concerns over data associated with multiple users, remaining privacy violations largely unresolved and leading to the potential disclosure of information that at least one user intended to keep private. In this paper, we propose an approach to enable collaborative privacy management of shared data in OSNs. In particular, we provide a systematic mechanism to identify and resolve privacy conflicts for collaborative data sharing. Our conflict resolution indicates a tradeoff between privacy protection and data sharing by quantifying privacy risk and sharing loss. We also discuss a proof-of-concept prototype implementation of our approach as part of an application in Facebook and provide system evaluation and usability study of our methodology.