NOTE: Since this post was written we've updated our APIs with a lot of changes. They're documented here. http://android-developers.blogspot.com/2016/01/using-google-sign-in-with-your-server.html We have also provided migration guidance for your apps. To understand up to date user experience for security, check this post: http://android-developers.blogspot.com/2016/05/improving-security-and-user-ex