Certificate is removed from the machine keyset when the application is closed

Question

I'm trying to deploy a certificate into a windows-my store in order to use it for SSL in IIS6.0. When the application is running I don't see any errors in SSLDiag output and everything works perfectly, but once I close the application SSLDiag shows an error:

#WARNING: You have a private key that corresponds to this certificate 
but CryptAcquireCertificatePrivateKey failed

I checked the machine keyset and noticed that after I close my application it removes the file with a key which was created. Here is the location I checked:

C:\Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys 

How can I preserve the create key file in a machine keyset?

Here is the code I'm using:

        using(var openFileDialog = new OpenFileDialog())
        {
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                var password = "password";
                var certificate = new X509Certificate2(openFileDialog.FileName, password, X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable);
                var keystore = new X509Store(StoreName.My, StoreLocation.LocalMachine);
                keystore.Open(OpenFlags.MaxAllowed);
                keystore.Add(certificate);
                keystore.Close();
            }
        }

I tried different variations of X509KeyStorageFlags, but the file is still removed from machine keyset once I close the app. Why the file is removed and how can I prevent it?

Answer 1

I found the solution:

certificate.PrivateKey.PersistKeyInCsp = true;

This lets the private key to remain in the machine key set. I suppose the key was removed when the X509Certificate2 object was freeing its resources.