易票联C#加密的方法

最近公司对接易票联的支付，我们会用到加密的地方；
签名加密：

X509Certificate2 privateCert = new X509Certificate2("文件地址", "密码", X509KeyStorageFlags.Exportable);
RSACryptoServiceProvider privateKey = null;
privateKey = privateCert.PrivateKey as RSACryptoServiceProvider;
RSACryptoServiceProvider privateKey1 = new RSACryptoServiceProvider();
//准备加密1
privateKey1.ImportParameters(privateKey.ExportParameters(true));
//准备加密2
byte[] data = Encoding.UTF8.GetBytes(postData);
//准备加密3
byte[] signature = privateKey1.SignData(data, "SHA256");
//准备加密4
//密文
string sign = Convert.ToBase64String(signature);