Steganography
Steganography is probably one of the most ingenious applications of cryptography of all time. Even though it is common belief that it is a more recent concept, the art of hiding top secret information amidst content (more often than not in pictures), the earliest traces of steganography date back to 440 BC. Essentially a security tool, it differs from ordinary cryptography in the sense that in the latter, the message is converted into indecipherable symbols or codes, the implications of which are known only by the author and decoders. Steganography, on the other hand looks like a rather normal message with the secret codes hidden in it with such caution that your average person will never know the difference! An interesting historical fact is, when the Romans wanted to conceal pieces of text, they used to inscribe them on tablets and then coat it with wax so as to effectively hide the message. And steganography has definitely kept up with the changing times.
In the age of computers, even modifying a few bits in a picture or an audio clip could facilitate the hiding of a significant amount of text very effectively. What strikes as brilliant is, this change from the original file would never meet the common eye (or ear)! A primary use of steganography is for copyright protection, which entails a concept known as digital watermarking. Apart from this, it also finds use in the military field where the security of top secret information is a matter of life and death of millions everywhere.
Here is an example of steganography is use. We used OpenStego, an open-source steganographic software to hide one image within another:
Image containing a hidden image.
Hidden image extracted from it.And as we can see, the effect is quite incredible. The second image is literally hidden within the first image!
However, as the saying goes, there are two sides to every coin. Steganography is said to have been the secret weapon behind the September 11 attacks, though there is no concrete proof for this fact.
Countering steganography may be hard, but not impossible. This is where Steganalysis comes in to the picture. It can be done in two ways- visual attack and statistical attack. The first approach deals with physically comparing the original file with the tampered one. This lacks complexity, but isn't always effective. The second one involves monitoring the variations in the pixel patterns or frequency distribution of the altered file in comparison to the original one.
All said and done, if the misuse of steganography was put to a stop, the world would be a safer place.
Reference
- What is steganography? - A Word Definition From the Webopedia
- http://www.webopedia.com/TERM/S/steganography.html
- Steganography Revealed by Kristy Westphal
- http://www.securityfocus.com/infocus/1684