public string Encryption(byte[] privateKey)
    {
        // Wczytanie klucza publicznego
        X509Certificate2 certificate = new X509Certificate2(Settings.Default.PublicKey);

        var testData = privateKey;
        using (var rsa = (RSACryptoServiceProvider)certificate.PublicKey.Key)
        {
            try
            {
                byte[] encryptedData;
                encryptedData = rsa.Encrypt(testData, false);
                var base64Encrypted = Convert.ToBase64String(encryptedData);

                return base64Encrypted;
            }
            finally
            {
                rsa.PersistKeyInCsp = false;
            }
        }
    }