Using pfx certificate to authenticate a webrequest

[Nelson Russa]

Hi,

i need to get some info from a website page that requires an
certificate.

Ive got the provided certificate installed in IE, and when accessing
the website page, it shows a window to select the client certificate
and then shows the page correctly.

Im trying to do this by code (C# aspnet), using webrequest.

The certificate is in an pfx file and does not require password. I've
exported the file using IE to DER encoded binary X.509 (.cer).

My code:

X509Certificate certificate =
X509Certificate.CreateFromCertFile(Server.MapPath( "file.cer"));
HttpWebRequest req =
(HttpWebRequest)WebRequest.Create("https://websiteurl");
req.Method="POST";
req.ClientCertificates.Add(certificate);

// ...
// here goes the request response read
// ...
I got this error:

System.Net.WebException: The underlying connection was closed: Could
not establish secure channel for SSL/TLS. --->
System.ComponentModel.Win32Exception: The message received was
unexpected or badly formatted at
System.Net.TlsStream.EndRead(IAsyncResult asyncResult) at
System.Net.Connection.ReadCallback(IAsyncResult asyncResult) --- End
of inner exception stack trace --- at
System.Net.HttpWebRequest.CheckFinalStatus() at
System.Net.HttpWebRequest.EndGetResponse(IAsyncRes ult asyncResult) at
System.Net.HttpWebRequest.GetResponse()....

Can anyone help about this subject? Is this the right newsgroup for
this kind of questions, or should i post in security group?

Best regards,
Nelson Russa