I have to implement Claims based Authentication for an existing web app. Is there a way we can implement this without having a separate STS Application. We need to do this within our Application. Can anyone direct me how we can do this?
probably not. if your current web application has not been created with the Claims Based Authentication initially and if you have used the Classic Mode Authentication instead, you will have to create a new Web Application. After you create the new Web Application
with the Claims Based Authentication, you can export the original site collections from the current web app and import them into the newly created web application.
there are not too many web-application related settings that you will have to reconfigure in case you are creating a new web application, so I would go this way.