You have been warned.
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:
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zip output.zip text.txt
put the .gif and the .zip file in that order in the same file:
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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:
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mv output2 pretty-picture.gif
Example1:
gif.zip- (8.49 KiB) Downloaded 25 times
Example2, rename this one as either a .zip or a .wav:
- zipped-soundfile.zip
- (57.45 KiB) Downloaded 19 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
- I'm simply not a nice person!
