title: ServiceSecurityContext.Current.WindowsIdentity.Name is null
body: <p>i'm using message security with a certificate authentication</p>
  
  <pre><code>        &lt;basicHttpBinding&gt;
              &lt;binding name ="customBinding"&gt;
                  &lt;security mode="Message"&gt;
                      &lt;message clientCredentialType="Certificate"/&gt;
                  &lt;/security&gt;
              &lt;/binding&gt;
          &lt;/basicHttpBinding&gt;
  </code></pre>
  
  <p>i'm trying to log client user name, when i do this:</p>
  
  <p>ServiceSecurityContext.Current.WindowsIdentity.Name</p>
  
  <p>i get null. how can i retrieve the client's user name while using this security mode?</p>