Smile Game Builder archives (sgbpack)

[wattostudios]

Wondering if anyone knows enough about encryption to work out how they do it for Smile Game Builder engine archives.

Older versions were just a ZIP file with a funny header and no compression - they're pretty simple to figure out.

Newer archives look very different, to me it looks like the files are XOR'd with a 16-byte repeating key, but each file in the archive might have a different key? In the example archive, the first file looks like it might use this key (\x1E\x20\x45\x1B\x14\x84\xC9\x8C\x53\xA5\x7C\x42\x7B\xA9\x62\xE9) and a file a little further on with this key (\x34\x7C\x25\xD5\xEE\x10\x2C\x2A\x4B\xE7\xE0\xAE\x83\xBB\x2B\x49)

I admit I'm no expert in encryption, so I could be totally wrong.

It looks like there is probably no compression, as there are whole sections of repeating characters that really should be easy to compress.

Is anyone able to help with this?

Sample archive (from game Monarch of Greed - Act 1) - https://drive.google.com/open?id=12A3UhodYRvFjaM9-F_SQQ5JTlmhyO0NC

Thanks for any help!

[aluigi]

It's weird indeed and it's not a xor key since the resulting data is still senseless.
It's not a block cipher too since most of the bytes in these "sequences" are often differents.
Apparently it's necessary to do some reverse engineering and it's not possible to guess it from the file.

[lisomn]

About sgbpack
First you need to replace the first 8 bytes with
"\x50\x4B\x03\x04\x14\x00\x00\x00"
Then use that algorithm to decrypt

Code: Select all

byte* ptr = 0x02;
int num = 0;
if (0 < buffer.Length)
{
   do
   {
   int num2 = (int)((byte)(num % 16));
   buffer[num] -= (byte)((int)num2[ptr] * num2);
   num++;
   }
   while (num < buffer.Length);
}

[aluigi]

The sample is no longer available, anyone can upload it or another encrypted sgbpack file for testing?

[blebloblas]

Here you are:

https://drive.google.com/file/d/1ncVHzNGi1UBgG4ctHj8pqqVJ0hNw4zmZ/view?usp=sharing

It's from game: Zero Spring Episode 2

[lisomn]

Decryption tool I made

[lisomn]

The sample is no longer available, anyone can upload it or another encrypted sgbpack file for testing?

hi aluigi Here is the decryption logic, can you create a bms version?
The bms script I made is a bit slow

program logic

Code: Select all

      auto bs=File(file_name,"rb+");
      ulong size=getSize(file_name);
      char[] magic=bs.rawRead(new char[6]);
      ubyte[] key=[72,9,20,154,48,169,84,225,0,8,14,9,20,60,66,70];
      ubyte[] header=[80,75,3,4,20,0,0,0];
      if(magic.dup == "SGBDAT")
      {
         int versionno=(bs.rawRead(new ubyte[1])[0]<<8)+bs.rawRead(new ubyte[1])[0];
         if(versionno!=0)
         {
            int versionno=(bs.rawRead(new ubyte[1])[0]<<8)+bs.rawRead(new ubyte[1])[0];
            auto wbs=File(file_name~".zip","wb");
            wbs.rawWrite(header);
            int num=0;
            ubyte[] buffe=bs.rawRead(new ubyte[(size-8).to!uint]);
            for(int i=0;i<(size-8);i++)
            {
               buffe[num]-=key[num%16];
               num++;
            }
            wbs.rawWrite(buffe);
         }
      }

[aluigi]

Thanks a lot, just made the script
http://aluigi.org/bms/sgbpack.bms

[gaugsroff2]

Thank you. Unfortunately both tools extract a zip with lots of files but the png/obj/ogg files inside can't be opened.

Example game: https://syukino.itch.io/euclyca-chronicles-lyla

More details: Seeking smile game builder extractors / Game exe states: SGB RPG Player 1.12.8.4 by SmileBoom Co. Ltd.

[aluigi]

Ok I rewrote the script from scratch, it can now be used to dump all the files without creating the ZIP first.

The problem was simply that the extracted files had a second encryption (so after decompression) and needed to be decrypted.

[Renneta]

Ok I rewrote the script from scratch, it can now be used to dump all the files without creating the ZIP first.

The problem was simply that the extracted files had a second encryption (so after decompression) and needed to be decrypted.

Can you help me? I want to translate one game on the SGB engine, but I'm not a programmer and can't open this type of archives.

---OK, no need more.