UPDATE: Data modification is now fully functional!So yesterday I decided to poke around the encrypted data files of GST:Y v1.08 out of boredom to see if I could somehow get the key to the encryption, since it's long been a major obstacle in creating a translation for the game. I noticed a repeating pattern of 40 bytes and figured it had been XORed with 00s, so I ran it over the file and, sure enough, it turned out to be the key. I was able to identify headers and the filename/size data at the end of the file, but was not able to extract the files successfully; this turned out to be a problem with the program I was using, which removed some data causing the files to become corrupt.
To solve the problem, I wrote my own small and dirty program in C++ to do the decryption, the source code of which can be found in a link below. To use it, compile and run the program with the data file you want to process as the first argument. The decoded file is created in output.dat (it always overwrites since I didn't add any safeguard, so be careful.)
From what I gather, these are the contents of each data file:
data1.dat - Images: Logo images (still messy?)
data2-1.dat - Images: Portraits
data2-2.dat - Images: Portraits, battle sprites
data2-3.dat - Images: Portraits, battle sprites
data3.dat - Images: Backgrounds, effects
data4.dat - Dialogue/Scripts
data5.dat - Dialogue/Menus/Scripts
data6-1.dat - Audio: BGM
data6-2.dat - Audio: BGM
data6-3.dat - Audio: BGM
data7.dat - Images: Backgrounds
data8.dat - Images: Units, icons
data9.dat - Images: Backgrounds
data10.dat - Data files
data11.dat - Data files: Animations
data12.dat - Data files
data12.dat - Audio: SE
Now that the game accepts the modified files, hopefully the translation can begin.
Links to the tools and instructions on how to use them:
http://pastebin.com/zKmeN0BV