Steganography-Wow,a nice technology!!!

Last week I had my department function(virtuoso).It was really cool and I worked for 2 events in the function.One was best manager and the other was Project presentation.Project presentation was my favourite and it was rocking.One of the project presented there was steganography.This term was relatively new to me.But my senior informed me that it was a very common project and it was used by Osama Bin Laden!!!This kindled interest in me to find more on this subject.This post contains some nice information on steganography such that,even a novice could understand!!!

Steganography is the art and science of writing hidden messages in such a way that no one apart from the sender and intended recipient even realizes there is a hidden message. By contrast, cryptography obscures the meaning of a message, but it does not conceal the fact that there is a message. Today, the term steganography includes the concealment of digital information within computer files. For example, the sender might start with an ordinary-looking image file, then adjust the color of every 100th pixel to correspond to a letter in the alphabet -- a change so subtle that no one who isn't actively looking for it is likely to notice it.

Image of a tree.

By removing all but the last 2 bits of

each color component, an almost

completely black image results. Making

the resulting image 85 times brighter

results in the image below.

Image extracted from above image.

Generally, a steganographic message will appear to be something else: a picture, an article, a shopping list, or some other message. This apparent message is the covertext. For instance, a message may be hidden by using invisible ink between the visible lines of innocuous documents.
The advantage of steganography over cryptography alone is that messages do not attract attention to themselves, to messengers, or to recipients. An unhidden coded message, no matter how unbreakable it is, will arouse suspicion and may in itself be incriminating, as in countries where encryption is illegal.Often, steganography and cryptography are used together to ensure security of the covert message.

Steganography used in electronic communication include steganographic coding inside of a transport layer, such as an MP3 file, or a protocol, such as UDP.