HELP Decrypting Lua files

Question

i'm trying to mod a game named : DDTank Mobile, which is on both Android & IOS. This game runs on cocos2d engine, the thing is the lua files are encrypted. I read somewhere to look for 'sign' at the beginning of each lua files, but this is what i find

The sign seems to be ��+ in utf-8. In hex it is : F8 8B 2B

I found that you can use IDA to look into the Binaries of the SO File and Find the encryption key in a function called ApplicationDidFinishLaunching, so I tried not knowing what to do. Here's the pseudo-code from IDA: https://pastebin.com/T0RxB6ML

In this function, there is a call to StartConfig::enter and inside it there is this function used XXTeaEncrypt::setXXTeaKeyAndSign, here's the pseudo-code from IDA: https://pastebin.com/SjdvsKya

Link to the APK : https://m.apkpure.com/ddtank-mobile/com.wan.ddten/ Some Lua files + lib (SO) files : https://mega.nz/file/LJ0EXKiQ#aRLpaed4LXV0fSg9AK9-5-kZYYvOoHo49ytbDV6dMuI

Answer 1

Update on this :

I managed to get through the obfuscated lua files by hooking the luaL_loadbuffer exported function from libengine.so using frida, and managed to dump the game code.

After that i built a lua wrapper around the game, which would execute my lua code. Short after this, I realized that this game has plenty of stuff server side, so I couldnt do anything 'edgy' like changing my fightpower, diamonds, tickets, even if I was to send some hacky net message, server would check, i mean fair enough.

I tried bypassing the payment request, that i saw while looking through lua files (PayCallBackModelEntity.lua)

Anyways, I think i'm dropping this, can't do much, was a great opportunity for me to learn though :)