Steganography
What is Steganography?
Steganography is the practice of hiding information in computer pictures or music and relies on the fact that digital images and MP3 music files are made up of thousands of pieces of binary code, which tell a computer to colour a pixel or produce a sound. Because so many small pieces of digital information are involved, a handful can easily be altered to convey secret messages, without changing the overall effect to the naked eye or ear.
Steganography is all about hiding information in a computer file by disguising it as something else. For example, you might have an innocent-looking text document but, if you were to take the first letter of each sentence, it would contain confidential information. Or you might construct a bitmap image in such a way that, if you were to look at it in an image editor, it would appear as a normal pretty picture, but if you were to take every 9th pixel and convert the bits into bytes, and then load those bytes into Word, you'd have some secret information.
. Steganography works by concealing information (i.e. a text file) in a place where no one would think of finding that type of data (i.e. an image file). An example of this in real life is when you hide your jewels in the freezer, because no one will think of looking for jewellery there. It works by hiding the data in spaces in the internal structure of the host file. The host file seems like a normal file of its type (if it is an image file, it will look normal, and act normal, it will open correctly on any viewer), and since no one will think to see the file in machine coding, the information it conceals remains hidden. Usually, steganography is not used to conceal large amounts of information, because excessive file size is a clear giveaway that something has been hidden in the file (a 2 MB. 200x200x16 JPEG file is clearly suspicious to almost anyone).
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