易票聯C#加密的方法

最近公司對接易票聯的支付，我們會用到加密的地方；
簽名加密：

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