Help me with encrypted data.pak file

[teusma]

It took me a while but I understood haha, thanks. the only downside is that the quickbms executable is 19.3 MB and compressed 3.79 MB, this will overshadow almost all the gain I will have by decrypting the data.pak. But do what you know...that's life. If someone could create a C++ program from this BMS script, the executable would not exceed 100kb....

[L33THAK0R]

Originally Posted by teusma

It took me a while but I understood haha, thanks. the only downside is that the quickbms executable is 19.3 MB and compressed 3.79 MB, this will overshadow almost all the gain I will have by decrypting the data.pak. But do what you know...that's life. If someone could create a C++ program from this BMS script, the executable would not exceed 100kb....

I had a read through the article you linked and the concept is a lot simpler than you think. Based off of the authors "java-like pseudocode" I whipped up a couple python scripts that "decrypt" and "encrypt" the data.pak file. What is actually happening is basic obfuscation, for even bytes, the value is divided by 2, for odd bytes, 255 is added, and then the value is divided by 2. Very simple stuff.

Even though I've only ever dabbled in python scripting, writing a C++ application proved to be quite simple, here's the source code:

#include <fstream>
#include <vector>
#include <cstdint>
#include <iostream>

uint8_t reencrypt_byte(uint8_t d) {
    return (d < 128) ? (d * 2)
                     : static_cast<uint8_t>(2 * d - 255);
}

int main(int argc, char* argv[]) {
    if (argc != 3) {
        std::cerr << "Usage: reenc <infile> <outfile>\n";
        return 1;
    }

    // Read input file
    std::ifstream fin(argv[1], std::ios::binary);
    if (!fin) { perror("Error opening input"); return 1; }
    std::vector<uint8_t> buf((std::istreambuf_iterator<char>(fin)),
                              std::istreambuf_iterator<char>());

    // Transform in place
    for (auto &b : buf) {
        b = reencrypt_byte(b);
    }

    // Write output file
    std::ofstream fout(argv[2], std::ios::binary);
    if (!fout) { perror("Error opening output"); return 1; }
    fout.write(reinterpret_cast<char*>(buf.data()), buf.size());

    return 0;
}

I've saved you the trouble of compiling this, attached in the zip file are both the python scripts as well as the C++ source code and application, as well as a copy of sfk + a batch script for patching all the extracted streams (well 1116/1139 files, but all WAV, OGG were found. 651/663 DDS found.), if you choose to go down that route. Good news is this solution meets your requirements, with just srep+lolz the compiled C++ executable goes from 131KiB to 34.9KiB. Hope this helps, this was a good excuse to keep some technical skills fresh.

[teusma]

Couldn't you (if it's not too much to ask) simply produce a tool that looks like this pak_enc_dec that can be put in a chain like this: -mpak_enc_dec+oggre+srep+msc+lolz.

To be honest, your program I don't understand how it works. and it also has a dependency on dlls - which is not a big problem since when compressed it drops from 1.50mb to 343kb...

Sorry if I'm being noob in any way.

[L33THAK0R]

Originally Posted by teusma

Couldn't you (if it's not too much to ask) simply produce a tool that looks like this pak_enc_dec that can be put in a chain like this: -mpak_enc_dec+oggre+srep+msc+lolz.

To be honest, your program I don't understand how it works. and it also has a dependency on dlls - which is not a big problem since when compressed it drops from 1.50mb to 343kb...

Sorry if I'm being noob in any way.

There shouldn't be a dependency on DLLs for the compiled executable. The usage is also plain to see when you run it from the command line. I'd advise running your own tests but I would think msc+oggre+lolz would be better suited, if you choose to not perform any post-install operations. Given how it would be a single command in a batch script to run the restoration for the data.pak I don't think any further development is warranted.

[teusma]

forget it, I managed to create myself (with the help of AI) a tool(with only 29kb) that can be used like this: -mpak+oggre+srep+msc+lolz reaching all types
of files inside the data.pak already decrypted. this ambition I had to make this repack was more for sport - because it doesn't save much
space - due to the amount of .ogg and .wav being small, but even so it was a delight to compress after applying the decryption.

I'll leave the tool here for anyone who wants to use it too: