Here is an example:
https://www.file-upload.net/download-127...0.png.html
Size: 17,6 kilobyte.
File extension: PNG
This is from Orc Castle, a PC game. Apparently, the game uses a special PNG version (?) to hide its graphics. Manual Pictures, cursors, etc. are displayed, but the rest can't be opened.
Is there any trick to it?
OK that's fricken weird. I was expecting there to just be some junk at the front of the file but it looks either compressed/encrypted or just a completely different format. Would you mind uploading a few more?
What I've gathered so far:
0x00: "EENC" header
0x04: File size after this point (little endian), i.e. file size - 8
So it has some structure at least. The extremely small sizes suggests compression though, which is bad news since I can't find anything on it online :\
Just what I thought, these are encrypted and used for hiding the original pictures. Here are some bigger ones:
Everything from 100-999 kilobytes:
https://mega.nz/#!gY5EQB4L!mCFa8dlfnwqnm...kHJMkc8X9o
Size: 114,9MB
File extension: PNG
By the way and just if it helps:
Here is a encrypted file with the name 00020100.png, this one is from me:
https://www.file-upload.net/download-127...0.png.html
And now this is the same file, but from the internet, decrypted and therefore viewable. It was also named 00020100.png and is an actual file from the game:
https://i.imgur.com/0yGGWiz.png
Someone on the internet was able to decrypt the compression, I already messaged him but I'm not sure if he responds. Could you take a closer look how he possibly did it?