title: Federated security using Thinktecture IdentityServer
body: <p>I have few mvc applications that are still in development and use Forms with SimpleMembership to register and authenticate users, these applications <strong>use same database</strong> and I have foreign keys all around to UserProfile table from simple membership.Recently I decided to give a shot to Federated security just to get SSO without reinveting the wheel, but there are few things I am confused about.</p>
  
  <p><strong>Should I set up Identity Server to use same database as my applications?</strong>
  (<em>Then I could somehow put userID in claims or something, so I know how to get information from other tables for this user, is this correct?</em>)</p>
  
  <p><strong>How is normal forms registration done when using federated security?</strong>
  (<em>I am thinking that registration could be done in any application, insert rows in tables which Identity server uses or adjust STS to user simple membership tables for authentication,is this correct?</em>)</p>
  
  <p><strong>Is it possible to authenticate users from each individual RP(mvc application) and still get SSO without redirecting user to STS?</strong> (<em>somehow with internat HTTP requests</em>)</p>
  
  <p>What happens when STS fails? Are users then unable to login to any application? Is there any solution to this?</p>