AceDecryptor

Program.cs

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

namespace AceDecryptor;

class Program
{
    private const string Pbkdf2Password = "u8DurGE2";
    private const string Pbkdf2Salt = "6BBGizHE";
    
    static void Main(string[] args)
    {
        Console.WriteLine("AceDecryptor - 2025 by nightshade");
        Console.WriteLine("Decryption tool for Phoenix Wright: Ace Attorney Trilogy encrypted asset files");
        if (args.Length == 0)
        {
            Console.WriteLine("Usage: AceDecryptor.exe <input file>");
            return;
        }

        var filePath = args[0];
        if (!File.Exists(filePath))
        {
            Console.WriteLine("Error: input file does not exist");
            return;
        }

        var fileBytes = File.ReadAllBytes(filePath);
        var outputBytes = Decrypt(fileBytes);
        
        File.WriteAllBytes(filePath + ".d", outputBytes);
        Console.WriteLine("Done!");
    }

    private static byte[] Decrypt(byte[] fileBytes)
    {
        var keyBlockSize = 128;
        
#pragma warning disable SYSLIB0022
#pragma warning disable SYSLIB0041
        
        var rijndael = new RijndaelManaged();
        rijndael.BlockSize = keyBlockSize;
        rijndael.KeySize = keyBlockSize;
        var deriveBytes = new Rfc2898DeriveBytes(Pbkdf2Password, Encoding.UTF8.GetBytes(Pbkdf2Salt));
        deriveBytes.IterationCount = 1000;

        rijndael.Key = deriveBytes.GetBytes(keyBlockSize / 8);
        rijndael.IV = deriveBytes.GetBytes(keyBlockSize / 8);
        using var decryptor = rijndael.CreateDecryptor();
        
        var decryptedBytes = decryptor.TransformFinalBlock(fileBytes, 0, fileBytes.Length);

#pragma warning restore SYSLIB0041
#pragma warning restore SYSLIB0022
        
        return decryptedBytes;
    }
}