title: Validate Windows Identity Token
body: <p>I am trying develop a simple web service to authenticate users of a desktop application using the windows identity framework, at present I am passing the token generated by <code>WindowsIdentity.GetCurrent().Token</code> via a post variable (it is encrypted and ssl'd,  Windows authentication is not an option given the layout of our domain's and the configuration of the server). I am passing the token back fine and converting it back to an <code>IntPtr</code>. </p>
  
  <p>I am at a lost as to how to validate the token to ensure that it was generated by a particular Active Directory (or any for that matter). I have tried to create a new <code>WindowsIdentity</code> instance given the token however that just results in an Exception (message: Invalid token for impersonation - it cannot be duplicated). </p>
  
  <p>If anyone can provide any help or even hints I would greatly appreciated, thanks in advance.</p>