The game was made with Unity. As such, its mostly comprised of .assets files, just like the PC version, with one particularity: the heaviest (and most important) assets have been compressed within a .psarc archive, a proprietary format used by Sony games since the PS3 era.

In 2020, I used a tool named Karameru to extract the .psarc archives. This time I used Noesis, a tool widely-used to preview 3D models from different formats, but also for extracting some types of archives, which .psarc is part of.

Once the archive is extracted, we can treat its contents like a usual Unity game folder. Unfortunately, this means more extracting and repacking but it won’t be a problem, as this time we have the whole Unity modding community behind our back!

My favorite tool for extracting Unity .assets files is AssetStudio, a software that has been faithful to me since 2019, when I first used it on the PC version of the game. It’s very easy of use for previewing and extracting the contents within the archives, but it unfortunately does not support reimporting/repacking.

Once the files we want are extracted, we can edit them to our leisure. I won’t elaborate much on this part, but one thing I can say is that AssetStudio does its best to convert the assets into commonly-used formats: .txt/.json files for the TextAsset files, .png files for the Texture2D ones, .wav for the AudioClip… Surely, we won’t have much research works to find software able to work with these file formats!

Anyway, after editing the extracted filed to our will, we will reimport them with a russian tool called UnityEX (YandexDisk mirror). Just like AssetStudio, it’s a tool I got familiar with in 2019, when I worked with the PC version. It has been helpful enough for me to donate to its developer in order to get all the features of the program, such as the Unity 2020-2021 support (more on that on the official forum thread), but we can work with the freeware version as well, since the game has been compiled with Unity‘s 2016-2017 SDK!

Unlike AssetStudio, UnityEX only opens one file at a time, which doesn’t matter since all the content we need is stored within the resources.assets file. When we open an archive within UnityEX, we can extract the files by right-clicking them, then by pressing “Extract with convert or Raw”: this will convert a file to a more common extension if it’s known (like AssetStudio does), or leave it as-is.

By hitting the “Import all files” button in UnityEX, the program will look all the files from the folder mentioned above, compare the filenames to the ones within the opened .assets archive, then replace each matching occurence. Any .png file is automatically converted into a .tex Texture2D file, then reinserted in the archive. If the program finds a filename that doesn’t correspond to anything in the archive, it will give a warning and askip if we want to continue anyway.

Now that the resources.assets has been edited, it’s time to do the whole process… Backwards! First, we need to repack the folder containing the extracted .assets files back to a .psarc file. This time, instead of Karameru, I used Total Commander, a freeware file manager which had the benefit of supporting .psarc repacking thanks to a third-party plugin by BEKETATA.

And… that’s it! Now, we have our modded archive.psarc file, ready to get inserted back into the game. As there are multiple ways of doing that, which both take a fair amount of time and dedication, I will document them in a final post, one that will get more focused on the PS4-side manipulation than the PC one.

In this post, I will go through the steps we must follow in order to play a modded game on a PS4:

• First of all, we need a FAT32 (or exFAT)-formatted USB Drive. 8GB should be enough for The Silver Case but the bigger, the better!

• As of the console, we need a jailbreakable PS4. Firmwares 5.05, 6.72, 7.02, 7.50~7.55 and 9.00 are compatible. If you’re on a lower firmware, you should upgrade to the latest exploitable version. If you’re on a higher firmware, you’re out of lock and need to wait for an exploit to be found. DO NOT TRUST THE “DOWNGRADER” SOFTWARES, IT’S A SCAM!

• If the console is compatible, we will need to run a HEN exploit on boot in order to enable the jailbreak functionnalities. This is done by running webkit exploits either from a local server (self-hosted exploits), or from a website that hosts them (example here). The most well-known HEN enablers are GoldHEN and MIRA, both give access to the functionnalities we need.

• Once the HEN exploit is active, we need to dump the original copy of the game, and it’s updates when needed. In order to do that, BinLoader must be enabled by going in the console’s Settings > Debug Settings > Servers Setting, and then ticking the checkbox here. Once enabled, we can run a Game Dumping exploit (the Karo menu linked earlier has it in the Dumper Group category). The next booted game will be dumped to the USB Drive plugged in the console. This process might take a while, maybe a bit less than an hour, but in the end we obtain a clean folder with all of the game’s files. This step is necessary as all the PS4 games are encrypted within PKG files locked by a passcode, and are only decrypted on runtime.

• At the end of the process, we have a CUSAXXXXX-app folder on your USB Drive. If the game has updates, we will end up with CUSAXXXXX-patch folders as well.

• The next step is rebuilding the dumped games (and updates) into Fake PKGs by using the Fake PKG Tools: we generate a .gp4 file for the base game with gengp4_app.exe, then we open the resulting .gp4 file within orbis-pub-gen.exe and click on the “Build” button on the top right corner. We then repeat the process for all the updates by running gengp4_patch.exe instead.

• We can then install the generated PKG files back on the PS4 by putting them on your USB Drive, then going into “Settings > Debug Settings > Package Installer”.

We are good to go! Now that our game has the default passcode 0000000000000000…0, we can finally install whatever modded files we want over it.