private string Sign(string data)
        {

            var cert = new X509Certificate2(File.ReadAllBytes(@"C:\\Test.pfx"), "11111", X509KeyStorageFlags.PersistKeySet);
            var rsa = (RSACryptoServiceProvider)cert.PrivateKey;
            var signature = rsa.SignData(Encoding.UTF8.GetBytes(data), new SHA1CryptoServiceProvider());
            return Convert.ToBase64String(signature);
        }