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Chapter 1
Introduction
1.1 Steganography
Steganography [34] is the art of hiding information within innocuous cover carriers in ways such
that the hidden message is undetectable. In Greek, „stego‟ means „covered‟ or „secret‟ and
„graphy‟ means „to write‟ and therefore, steganography becomes “covered or secret writing”.
The information to be hidden is embedded into the cover object which can be a text matter, some
image, or some audio /video file in such a way that the very existence of the message is
undetected by maintaining the appearance of the resulted object exactly same as the original. The
main goal of steganography is to hide the fact that the message is present in the transmission
medium.
1.2 Steganography vs. Cryptography:
Cryptography [35] is the science of encrypting data in such a way that one cannot understand the
encrypted message, whereas in steganography the mere existence of data is concealed, such that
even its presence cannot be noticed. Using cryptography might raise some suspicion whereas in
steganography the existence of secret message is invisible and thus not known. We can think of
steganography as an extension of cryptography, and it is commonly used under the
circumstances where encryption is not allowed.
1.3 Types of steganography
On the basis of cover object steganography may be of many types like Audio Steganography,
Video Steganography, image Steganography etc. Image Steganography is very popular because
of popularity of digital image transmission over the internet. Image Steganography use
redundancy of digital image [2, 11] to hide the secret data. It may be divided into two categories.
They are spatial-domain methods and frequency-domain ones. In the spatial domain, the secret
messages are embedded in the image pixels directly. In the frequency-domain, however, the
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