I have an ASP NET web server application that calls another process running on the same box that creates a pdf file and returns it. The second process requires a secure connection via SSL.

The second process has issued my ASP NET application with a digital certificate but I still cannot authenticate, getting a 403 error.

The code is a little hard to show but here's a simplified method ...

    X509Certificate cert = X509Certificate.CreateFromCertFile("path\to\cert.cer");
    string URL = "https://urltoservice?params=value";
    HttpWebRequest req = HttpWebRequest.Create(URL) as HttpWebRequest;
    req.ClientCertificates.Add(cert);
    req.Credentials = CredentialCache.DefaultCredentials;
    req.PreAuthenticate = true;
    /// error happens here
    WebResponse resp = req.GetResponse();
    Stream input = resp.GetResponseStream();

The error text is "The remote server returned an error: (403) Forbidden." Any pointers are welcome.