The book aims at presenting novel research in the areas of social identity and security when using mobile platforms. The topics will cover a broad range of applications related to securing social identity as well as the latest advances in the field, including, the presentation of novel research methods that are in the service of all citizens using mobile devices. More specifically, academic, industry-related and government (law enforcement, intelligence and defence) organizations, will benefit from the research topics of this book that will be covering the concept of identity management and security using mobile platforms from various perspectives, i.e. whether a user navigates to social media, access their own phone devices, access their bank accounts, uses online shopping service providers, access their personal documents or accounts with valuable information, surfing the internet, or even being a victim of cyberbullying (being harassed, threatened, embarrassed, or targeted by another person). In all of the aforementioned cases, there is a need for mobile related technologies that protect the users’ social identity and well-being in the digital world, including the usage of hard and soft biometrics (on demand user authentication using face, iris, fingerprints, as well as marks, scars and tattoos), cybersecurity software and tools, active authentication algorithms (continuous vs. on demand user authentication), and identity anti-spoofing algorithms (e.g. liveness detection, fake document ID detection etc.). The book will cover all these topics and more by inviting experts from each of the discussed fields of interest.