Need help decrypting Il2CPP'd HCA files by Drawrgon at 8:20 AM EST on February 24, 2022
Hello,
I spent the last 13 hours to get the game of Digimon ReArise on Android decrypted. The game will close its servers in a few weeks, I was eager for the OST for years by now with no luck.
I had around 8 hours of fun getting the HCA key out of the game, spent another few hours on trying to get the HCA/ACB files decrypted, with no success. Whatever tool I found and tried, can't decrypt the files because they're either expecting two separate 8 Byte keys or simply don't return a result.
I packed the files I gathered into an archive, including the unpacked APK, the dump.cs from Il2CPPDumper with the DummyDLLs, a screenshot from AssetStudio's CriWareInitializer contents, two plain text files with the plain key and the key converted to Hex, along with a bunch of encrypted HCA files from the Cache, which the game only seems to load on several triggers during the main story and two ACB/AWB packs with HCA content that are present in the main APK.
VGMToolbox r1040 recognizes the ACB/AWB files and the files I tested from the Cache and extracts valid HCA files out of them, but they're garbled. I didn't find a way to specify a decryption key there, so I now ended up asking the experts gathering in this place.
Are there any programs available to decrypt newer versioned HCA files? I know vgmstream can play encrypted files, but I wouldn't mind decrypting them for myself. If you need anything else, let me know.
I'll add the key later, but you can make it playable in vgmstream if you make a ".hcakey" file with the key in binary (not text) form and put it with the .awb.
For example (unzip first): https://www.sendspace.com/file/46hvi6
However, it seems to only work with the .awb files. The Audio assets from the Cache folder can't be played (or decrypted?), even if I give them a .hca extension and place the same .hcakey file in the appropriate folder. Opening in NPP gives the same AFS2 header that the AWB file has, so it seems to be valid. What am I missing there?
Edit: Eh, it seems to work if I give them the .awb extension, that's interesting.
So, I noticed that half of the files in the Cache folder are actually ACB files. Problem is, they're named differently from the other AWB files. Is there a way to find out which belongs to which? I can read some parts of the ACB in NPP or Hex Editors, but that doesn't help me much, as it's probably only the table structure inside.
Edit: I can read the ACB so much that it's possible to get a slight hint of how many sub-indexes an AWB file has to have - at least when the files are actually consecutively numbered in the ACB file. I can work with that, but it would still be nice if an easier way existed.
Damn, you're a wizard. How does that work? I spent the last hours sorting files by hand and eventually gave up just now because it's impossible to separate the mainskill stuff.