Accessing Securised Web Service

I need to connect to a provider's web service with a Windows Form application. He gives me a certificate to access it but I have a security problem.

I have done these following steps : 开发者_StackOverflow中文版

1. Add certificate to personal store (on IE & Firefox)
2. Generate a proxy with the remote wsdl (no problem)

3. Use this code to call a method :

   `using (service1.MessagesService m = new service1.MessagesService()) {

   X509Certificate crt = new X509Certificate(@"C:\OpenSSL\bin\thecert.p12",string.Empty);

   m.ClientCertificates.Add(crt);

   var result = m.AuthoriseTransaction(aut);

   this.textBox1.AppendText(result.id.ToString());

   }`

I have the following error :

The underlying connection was closed: Could not establish trust relationship for the channel SSL / TLS.

Thanks for your help

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Your connection isn't being authorised correctly, is the webservice over https? You may need to create a custom implementation of CertificatePolicy. See this article for an example.