One of the reasons that intruders
can be successful is that most of the information they acquire from a system is
in a form that they can read and comprehend. Intruders may reveal the
information to others, modify it to misrepresent an individual or organization,
or use it to launch an attack.
One solution to this problem is,
through the use of steganography. Steganography is a technique of hiding information
in digital media. In contrast to cryptography, it is not to keep others from
knowing the hidden information but it is to keep others from thinking that the
information even exists.
Steganography is the art of
concealing information in ways that prevent the detection of hidden messages. The
goal of steganography is to avoid drawing suspicion to the existence of a
hidden message. This approach of information hiding technique has recently
become important in a number of application areas.
This is a major distinction
between this method and the other methods of covert exchange of information
because, for example, in cryptography, the individuals notice the information
by seeing the coded information but they will not be able to comprehend the
information.
However, in steganography, the
existence of the information in the sources will not be noticed at all. Most
steganography jobs have been carried out on images, video clips ,texts, music
and sounds .Nowadays, using a combination of steganography and the other
methods, information security has improved considerably. In addition to being
used in the covert exchange of information, steganography is used in other
grounds such as copyright, preventing e-document forging.
A classical steganographic
system’s security relies on the encoding system’s secrecy. An example of this
type of system is a Roman general who shaved a slave’s head and tattooed a
message on it. After the hair grew back, the slave was sent to deliver the now-hidden
message. Although such a system might work for a time, once it is known, it is
simple enough to shave the heads of all the people passing by to check for
hidden messages—ultimately, such a steganographic system fails
Modern steganography attempts to
be detectable only if secret information is known. For steganography to remain
undetected, the unmodified cover medium must be kept secret, because if it is
exposed, a comparison between the cover and stego media immediately reveals the
changes.
Embedded information in a JPEG. (a) The unmodified original picture; (b) the picture with the first chapter of The Hunting of the snark embedded in it
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