The last few years have witnessed a significant growth in the number of identity management solutions. Because of the nature of the information that is handled by such systems, and because of their potential ubiquity, privacy and practicality issues are of great importance for such schemes. This book aims to provide an academic overview of the concepts of identity and identity management. It focuses on two categories of identity management systems, namely Information Card-based (ICIM) and Federated identity management systems. In addition to that, two novel schemes to enhance the privacy of identity management systems are given. The first aims to improve the privacy of ICIM systems, and the second aims to enhance user authentication within by adding an additional authentication layer. With regard to practicality, the book presents two novel schemes designed to enhance the practicality of identity management systems. The first enables the integration of ICIM and Federated identity management systems; whereas the second scheme aims to enhance the practicality of Federated identity management systems by introducing a framework for delegation services.