You must have played with a pen which releases ink which is not visible to our naked eye. It was only visible to us after glowing torch (that was on that pen) over the text which we had written with that pen. No one could get idea that we had written a hidden text unless given a hint. We used to do that for fun or for giving someone a personal message .Likewise we can hide data in images in Bitmap(bmp),Gif image,mp3 and pdf files. This technique of hiding data is known as Stegnography.
Why Stegnography is used? There can be several reasons for doing this. Few of them are:
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