Some Windows Phone applications will need to identify the user. Most Windows Phone users have a Windows Live ID. So, leverage that Windows Live ID. How? Use OAuth2.
In June 2011, the Windows Live Developer platform added OAuth2 to seamlessly access Live Id, Hotmail, Calendars SkyDrive, and other Windows Live Assets. There’s a showcase site you should check out.
OAuth2 puts the user in charge of what applications are allowed to access. We have branded this “Windows Live Connect”. It is for web, desktop, and mobile applications. Today, we’ll discuss how to integrate Live Id into your Windows Phone application.
Read the whole article here.