Social Network Sites play an increasingly important role in both personal and professional life. Evolving to a ubiquitous medium for social interaction, they have changed the way people keep in touch with close and spatially distant contacts and communicate with each other in a semi-public environment. Due to their increasing pervasiveness and dependence on personal data, the emergence of Social Network Sites has been accompanied by privacy concerns. Firstly, these concerns target the prevalent oligopolistic landscape, with few service providers of centralized Social Network Sites having access to millions of user profiles. Secondly, privacy is increasingly threatened by an individual's contacts on Social Network Sites. Users struggle with presenting favorable images of themselves to particular contacts while at the same time preventing other contacts from gaining access. As a consequence of these Social Identity Management challenges, personal data is often visible to a larger than intended audience, including contacts such as an individual's employer.This book gives insight into a privacy-preserving infrastructure that allows for managing social identities in a privacy-preserving and service provider-independent manner. It combines the privacy advantages of decentralization to protect against Social Network Site service provider profiling with the users' technical needs to put privacy preferences into practice for protection against other Social Network Site users. Based on the fundamental idea of separating social identities from infrastructural services, an autonomous identity provider as the core of this proposal supports a user's Social Identity Management activities, intensively drawing upon automation and visualization techniques. To complete the infrastructure, integration mechanisms leveraging existing web standards are developed to deploy autonomously managed identities on existing Social Network Sites.