Social networking: Security, privacy, and applications

Online social networks have become ubiquitous and changed the way that users interact online. There has been an enormous growth in the usage of online social networking in the past few years as users share a variety of information including personal profiles, pictures, and messages to socialize with their friends in the Internet. Besides, several special purpose social networks have emerged to serve their users with useful functionalities. This vast amount of user data is valuable, and therefore, introduce several security and privacy risks and challenges.;In this thesis we propose several techniques to enhance the security and privacy features of online social networks. Our goal is to shift the control over user data from a centralized social network provider to the end users. We realize this concept by decentralization of the social networking architecture. First, we construct and implement a cryptographic access control mechanism that ensures data confidentiality and integrity, and efficiently supports the fine-grained access policies expected by social network users. Next, we present a detailed design of a decentralized online social network that focuses on security and privacy. Finally, we propose and implement auditable anonymity, a cryptographic scheme, which allows a social networking user to keep track of who accesses her data even when her data is encrypted and decentralized, without revealing this information to the storage provider.