title: Single Sign On for only part of users?
body: <p>For a few days have I been struggling with research on Single Sign On mechanism in ASP.NET, however I still cannot find an answer to a problem which I need to solve. I've read several articles about the mechanism (including <a href="https://www.simple-talk.com/dotnet/asp.net/introducing-single-sign-on-to-an-existing-asp.net-mvc-application/" rel="nofollow">https://www.simple-talk.com/dotnet/asp.net/introducing-single-sign-on-to-an-existing-asp.net-mvc-application/</a> and <a href="http://www.codeproject.com/Articles/106439/Single-Sign-On-SSO-for-cross-domain-ASP-NET-applic" rel="nofollow">http://www.codeproject.com/Articles/106439/Single-Sign-On-SSO-for-cross-domain-ASP-NET-applic</a>), but think that I either cannot fully understand how it works or I am looking for a wrong thing.</p>
  
  <p>If I understood well, Single Sign On is a mechanism which allows to authenticate a user across all connected web applications with single credentials. However, what I need to do is to allow only some users from application A to access some features in application B by clicking a hyperlink (because only some users will have account in both applications). Both applications should have an independent login mechanism (because some users should have access to only one of the applications), but when the user loggs in the application A and have an account in application B, he should be signed in both apps (not necessarily the other way round).</p>
  
  <p>And here comes the question: is single-sign-on with centralised authentication really what I need here? And if yes, how could I use it only for some of users? I'd be very grateful if someone could explain it to me or provide a source, where I can find more information about it.</p>