签名加密字符

public static string SignData(string PlainData)
{
    byte[] bytes = Encoding.Default.GetBytes(PlainData);
    X509Certificate2 certificate = new X509Certificate2(ConfigurationSettings.AppSettings["pathpfx"], ConfigurationSettings.AppSettings["passwordpfx"]);
    byte[] rgbHash = new MD5CryptoServiceProvider().ComputeHash(bytes);
    RSAPKCS1SignatureFormatter formatter = new RSAPKCS1SignatureFormatter();
    formatter.SetKey(certificate.PrivateKey);
    formatter.SetHashAlgorithm("MD5");
    return ToHexString(formatter.CreateSignature(rgbHash));
}