That does look promising, thanks for sharing it! I will definitely try it out when I am free!
Your example of decrypting a ToCS save file and seeing it on your vpk installed game is particularly relevant to a issue I am currently facing so hopefully you could me out on this?
I own a legit cart of ToCS (PCSE00786, no DLC installed) with tons of save files but tried installing and running a vpk backup version I got online for test purposes, only to find that I couldn't even start the game anymore as I got a C0-11138-4 (The file is corrupt) error as apparently the ToSC vpk somehow installed onto the same circle as my cart instead of generating a new one. I couldn't transfer the game data via QCMA after that so the best I could do was to access ux0:user/00/savedata/PCSE00786 and ftp the files over to my PC. I then deleted the game circle from my vita and the PCSE00786 file from ux0:app/
I reinstalled the game using my physical cart and played through the beginning so that I could save (I made 3 save files to test what files would write in ux0:user/00/savedata/PCSE00786 and the new files that showed up were save000.dat, save001.dat, save002.dat, save255.dat, thumb000.png, thumb001.png, thumb002.png and thumb255.png
I then ftped the matching backup files (save000-002, 255, thumb000-002, 255) I had on PC to the Vita, overwriting them. Unfortunately, this only broke the saves such that when I tried to load them again, they gave me an error.
Since that didn't work, I restarted from scratch by deleting the game circle again, repeating the beginning and creating save files, but this time I replaced the entire ux0:user/00/savedata/PCSE00786 with my backup. After doing this, I could not even start the game as I got the C0-11138-4 error again.
I am seriously at a loss as to what I should do to get my save files working again. After investing 70+ hours and being so close to clearing the game, words can't describe how crappy I would feel if I had to restart from scratch so if there's a way I could use those save files I extracted (if they are even useful at this point in time since I don't know if they were corrupted as well by the time I copied them), I would be really grateful! I took a look at the decrypting tutorials you mentioned but there are some steps that I think I am unable to follow because of the special circumstances I am currently in for ToSC...