Shadowverse card master decryption

Program.cs

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace CardMasterDecompile
{
    class Program
    {
        static void Main(string[] args)
        {
            // string cardMasterFilePath = args[1];
            string cardMasterFilePath = "card_master_1";
            Console.WriteLine(File.Exists(cardMasterFilePath));
            using (StreamReader reader = new StreamReader(cardMasterFilePath))
            {
                reader.ReadLine();
                string output = DecryptRJ256(reader.ReadToEnd());
                File.WriteAllText("card_master.csv", output);
            }
        }

        public static string DecryptRJ256(string prm_text_to_decrypt)
        {
            string result;
            using (AesManaged aesManaged = new AesManaged())
            {
                string text = prm_text_to_decrypt.Substring(0, 32);
                string s = text.Substring(0, 16);
                string s2 = prm_text_to_decrypt.Substring(32);
                aesManaged.BlockSize = 128;
                aesManaged.KeySize = 256;
                aesManaged.Key = Encoding.UTF8.GetBytes(text);
                aesManaged.IV = Encoding.UTF8.GetBytes(s);
                aesManaged.Mode = CipherMode.CBC;
                aesManaged.Padding = PaddingMode.PKCS7;
                byte[] array = Convert.FromBase64String(s2);
                using ICryptoTransform cryptoTransform = aesManaged.CreateDecryptor();
                byte[] bytes = cryptoTransform.TransformFinalBlock(array, 0, array.Length);
                string @string = Encoding.UTF8.GetString(bytes);
                aesManaged.Clear();
                result = @string;
            }
            return result;
        }
    }
}