title: ASP.NET Web API - NTLM authentication and HTTPS
body: <p>I have the following configuration:</p>
  
  <ol>
  <li>self-hosted ASP.NET Web API</li>
  <li>ASP.NET MVC 3 web application</li>
  </ol>
  
  <p>Web app [2] comunicates with Web API [1] over HTTPS.
  They both (for now) live on the same machine.</p>
  
  <p>Http binding for the Web API [1] is configured like that:</p>
  
  <p><code>httpBinding.Security.Mode = HttpBindingSecurityMode.Transport;</code>
  <code>httpBinding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Ntlm;</code><br/>
  <code>httpBinding.TransferMode = TransferMode.Streamed</code></p>
  
  <p>I cannot make it work using https AND ntlm authorization.</p>
  
  <ul>
  <li>If I communicate over plain http it works and I'm properly authenticated</li>
  <li>If I communicate over https it gives me "401 Unauthorized" error for all controller actions which have [Authorize] tag (it works for actions which do not require authorization though)</li>
  </ul>
  
  <p>Why changing ONLY the transport protocol (from http to https) stops NTLM authentication from working?</p>
  
  <p>Thanks for any help with that!</p>