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Encrypted unity3d files

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Nanoka
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Encrypted unity3d files

Post by Nanoka » Mon Jan 13, 2020 2:25 am

Hello, I dumped files from a mobile game for extraction but apparently most are encrypted.
Files are unity3d. First of all I checked if it was consistent across all encrypted files but the only consistency I found was the first 3 bytes with text "EAB" followed by other encrypted bytes instead of the expected "UnityFS", though the version apparently isn't encrypted.
Searching the web all I found is that some guy on 2ch wrote a program for decrypting this but the link is dead and there is no information about the process or anything except what I already know.
I have no knowledge on encryption, so I come here looking for any help.

Here is a zip with a bunch of files, some encrypted and others not, from the same game:
https://mega.nz/#!U8pECSyB!-jy03DT1fLGB ... A0NL_Z9Yk0

Thanks in advance!

Edit:
After getting part of a decrypted file by dumping the game memory and comparing with the encrypted counterpart I have some findings.

First of all, the encryption stops at some point and this address is right here:
Image
It is stored in little endian at 0x04 and is 2 bytes long.

Next, how (I think) this encryption works:
Image
The first byte at 0x60 is XORed with the value from 0x06.

Then every next byte is XORed with the previous XORed byte and stops before the stored address at 0x04.

Dumped decrypted file:
Image
Encrypted file:
Image
XOR 0x61 with 0x60:
Image
Then XOR 0x60 with 0x06:
Image

Now I need help with writting a script for this or something.

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chrrox
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Re: Encrypted unity3d files

Post by chrrox » Tue Jan 14, 2020 3:13 am

What game is it?

Nanoka
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Re: Encrypted unity3d files

Post by Nanoka » Tue Jan 14, 2020 6:18 am

This is from girls und panzer mobile game.

I have actually wrote a windows batch file using some other utilities I found on the web and got myself a way for doing this by just running it.
While it worked for all files, it is a mess and needs so many external executables with their dependencies its inconvenient to hand it to somebody else.

If you want to take a look, I attach a zip with bat and some of the executables.
gup_eab.zip
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