Kartrider Rushplus - encrypted unity3d files

[Driftdslash]

Hi, I have been ripping a game called Kartrider Rushplus. I heard that the files from the client has been secured more hardly since there were many people attempting to rip and make game hacks in this game. And i don't know if it is due to this policy, but the client of the game has been divided into 2 obb files since 1.6.8 version: the 1st one seems like original game client and other one is the update data. I could not open files in both of them. Well, I did rip the obb file, and I saw tons of mesh in both of them. The files were all unity3d files. Except that I couldn't process calling them in Unity Asset Studio. When I try to open them, they just don't come up and only one asset comes up which is non exportable and also invisible in the assets list. I am sure that these are all meshes and if I can manage to open this files, we are able to rip this game's models to latest versions. Can anyone do a research or find a way to open these files? (I used xapk/obb files to rip this game, not apk. Since I used apk to rip this game, none of the models came out.) And I resaerched and managed to find out that the files were encrypted in FBAU encryption. What is it? And how can I decrypt or extract files from it?