问X509Certificate2崩溃IIS

EN

        var cert = new X509Certificate2();
        cert.Import(Resources.wildcard, "xxx", X509KeyStorageFlags.Exportable);

        var cert = new X509Certificate2();
        cert.Import(Resources.wildcard, "xxx", X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable);

n exception of type 'System.Security.Cryptography.CryptographicException' occurred in mscorlib.dll but was not handled in user code
Additional information: Invalid provider type specified.

public class RsaSha1
{
    private readonly X509Certificate2 _certificate;

    public RsaSha1(X509Certificate2 certificate)
    {
        _certificate = certificate;
    }

    public string Sign(string signatureBaseString)
    {
        return SignCore(signatureBaseString);
    }

    string SignCore(string baseString)
    {
        using (var hash = Hash(baseString))
        {
            return Base64Encode(Sign(hash));
        }
    }

    private static string Base64Encode(byte[] signature)
    {
        return Convert.ToBase64String(signature);
    }


    private byte[] Sign(SHA1CryptoServiceProvider hash)
    {
        var formatter = new RSAPKCS1SignatureFormatter(_certificate.PrivateKey).
            Tap(it => it.SetHashAlgorithm("MD5"));
   //The line above throws the Exception if X509KeyStorageFlags.MachineKeySet is added,
   //but without X509KeyStorageFlags.MachineKeySet my application works in a console application (stress testing) but not in IIS (in a web application)
        return formatter.CreateSignature(hash);
    }

    SHA1CryptoServiceProvider Hash(string signatureBaseString)
    {
        var sha1 = new SHA1CryptoServiceProvider();

        var bytes = Encoding.ASCII.GetBytes(signatureBaseString);

        using (var crypto = new CryptoStream(Stream.Null, sha1, CryptoStreamMode.Write))
        {
            crypto.Write(bytes, 0, bytes.Length);
        }

        return sha1;
    }
}