Fun with zip files!

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Fun with zip files!

Postby dagon on Mon Jul 09, 2012 12:09 pm

The geek factor of what you're about to read is probably close to redefining 'geek'.
You have been warned. :shock:

Here goes...
As a zip file has it's specifications in the end, while most other files has it in the beginning(header), you can concatenate a zipfile in the end of another file if that file has a header that defines it's length (.gif, .wav, ... you name it!). This way all you need to do is to rename it *.zip for the OS to read it as an archive or, as a .gif(if that's what you've got) to open it as a picture. In the case of Linux, omit the suffix and the OS will read the magic numbers in the beginning of the file and treat it accordingly.


In short, this is how you do it:
zip a text file:
Code: Select all
zip output.zip text.txt


put the .gif and the .zip file in that order in the same file:
Code: Select all
cat picture.gif output.zip > output2


Now, if you want to present someone with the pretty picture containing a hidden message you rename the file as a picture:
Code: Select all
mv output2 pretty-picture.gif


Example1:
gif.zip
(8.49 KiB) Downloaded 38 times

Example2, rename this one as either a .zip or a .wav:
zipped-soundfile.zip
(57.45 KiB) Downloaded 31 times


Here is where I got this stuff. I only made a more general interpretation of it and "tutorialised it".
http://gayhacker.wordpress.com/2009/04/ ... well-well/
http://www.cs.cmu.edu/~dst/DeCSS/Gallery/Stego/index.html

8) - I'm simply not a nice person!
Last edited by dagon on Mon Jul 09, 2012 5:52 pm, edited 2 times in total.
Reason: Changed to a less elusive title.
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Re: Fun with zip files!

Postby remoulder on Mon Jul 09, 2012 4:58 pm

Ho not very nice geek, methinks you made a boo boo in your cat example :lol: :lol: :lol:
[Edit] your original post and add [SOLVED] once your question is resolved.

“The people are my God” stressing the factor determining man’s destiny lies within man not in anything outside man, and thereby defining man as the dominator and remoulder of the world.
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Re: Fun with zip files!

Postby dagon on Mon Jul 09, 2012 5:57 pm

Fixed, I think... 8)
I found it crazy hard to keep track on what thing went were and why on this one...
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