Steganography

Hey everyone, I’m on a challenge where I have a png image with detected errors (if pngcheck is correct). I also have a .bin file that I read as hexadecimal and I was able to find PLTE inside (a critical chunk for png images). however, I’ve no clue how to assemble both files. I’ve read some documentation about png chunks but I don’t think I’ll find the answer there. Any hint for me?  😄

Thanks !

You should start with inspecting chunks in png image. You will find some hidden metadata in one of them which will help you to generate new image.

So I stacked with this new image. It seems that key on this image is fake and I need to do something with this generated image and second bin file. I think that I need to concat this two files but as Victor I don’t know how to do it. The problem in bin file because it contains some data before PLTE chunk (is it rubbish?) and according to png specs and bytes before PLTE this chunk have 6 byte size (sounds like bullshit). Can someone give a hint what to do next?

P.S. PLTE chunk is critical only for images which have color type 3. And it seems that our image have color type 2.

You are both asking good questions, but this one will take time and patience. :)

You might look over the PNG specification and ask yourself what the minimum set of chunks would be for a viable image. Also, what might someone have "altered" that you could undo with sufficient understanding????