This authoritative guide offers you a detailed look at OpenID and OAuth, two emerging technologies for universal digital identity and data access. With these open specifications, not only can you provide customers with easier and more secure access to your site, you can also reduce costs and complexity associated with account maintenance. OpenID enables visitors to easily reuse an existing account for many websites including yours, while OAuth provides a consistent and secure way to share personal data. "OpenID: The Definitive Guide" offers best practices, step-by-step instructions, and clear examples to help you implement OpenID, OAuth, or both.Written by some of the original creators of these protocols, this book will help you: learn about identity on the Web, and why OpenID and OAuth were created; apply these technologies to everyday web scenarios; design your site's user experience to accommodate these technologies; understand how OpenID and OAuth complement one another; discover how businesses are using both technologies today; learn how these technologies fit into emerging reputation and relationship layers; know what can go wrong when using authentication technologies; and, delve into the technology that underlies OpenID and OAuth, and survey other related technologies. Support for reliable third-party authentication is gaining momentum, and many large corporations such as Google, Yahoo!, IBM, Microsoft, Flickr, and MySpace have already adopted OpenID or OAuth. This book will give you a firm grounding in these emerging and exciting digital identity technologies.