Sunday, February 7, 2010

Steganography - Some new fun

After reading an article in Linux Magazine, I've been playing with the steghide program available on most linux distros and popular repos.  I am quite impressed with this programs ability to insert quite a bit of information into an image or wav file.

The word steganography is of Greek origin and means "concealed writing" (citation wikipedia).  Really, as a word it is just describing covert messaging.  It offers no context in which it must occur or any kind of standard.  This technique is designed to put the message in a quite public place, kind of like the symbology clues you might have heard about in "The DaVinci Code".  The concept of security through obscurity is primary here.

The program recodes color codes in a jpg file to replace a shade of color with another and then uses the digit difference to insert the message.  The steghide program actually takes the image and the message and shuffles them together on the level of the data.  The receiver would NEED to know to look for the message since there is no visible indicator of a hidden message.

The application steghide is a command line tool.  There is a gui tool called steg-gui, but I didn't feel like compiling it, and since not in my repos I didn't use it yet.  So I won't offer any opinion of it here, maybe in the future if it can manage to be included in the repos.

As another example.  The image of Bettsy above, is also a steganograph.  Feel free to have a go and treat the image like a captcha.  After steghide is installed the following will produce the message that is this blog post, give it a try.

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