Providing authentication and authorization is de facto for web applications. We'll discuss authentication and authorization in this section. The new paradigm that has evolved over the past few years is OAuth. We'll learn and use OAuth 2.0 for implementation. OAuth is an open authorization mechanism, implemented in every major web application. Web applications can access each other's data by implementing the OAuth standard. It has become the most popular way to authenticate oneself for various web applications. For example, on https://www.quora.com/, you can register and log in using your Google or Twitter login IDs. It is also more user friendly, as client applications (for example, https://www.quora.com/) don't need to store the user's passwords. The end user does not need to remember one more user ID and password.
