04-10-2012, 11:01 AM
A Tutorial Review on Steganography
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ABSTRACT
The growth of high speed computer networks and that of the Internet, in particular, has increased the
ease of Information Communication. Ironically, the cause for the development is also of the apprehension
- use of digital formatted data. In comparison with Analog media, Digital media offers several distinct
advantages such as high quality, easy editing, high fidelity copying, compression etc. But this type
advancement in the field of data communication in other sense has hiked the fear of getting the data
snooped at the time of sending it from the sender to the receiver. So, Information Security is becoming
an inseparable part of Data Communication. In order to address this Information Security,
Steganography plays an important role. 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. This paper is a tutorial review of the steganography techniques appeared in the literature.
INTRODUCTION
The desire to send a message as safely and as securely
as possible has been the point of discussion since
time immemorial. Information is the wealth of any
organization. This makes security-issues top priority
to an organization dealing with confidential data.
Whatever is the method we choose for the security
purpose, the burning concern is the degree of
security. Steganography is the art of covered or
hidden writing [1]. The purpose of steganography is
covert communication to hide a message from a third
party.
Steganography is often confused with cryptology
because the two are similar in the way that they both
are used to protect important information [34]. The
difference between the two is that Steganography
involves hiding information so it appears that no
information is hidden at all. If a person or persons
views the object that the information is hidden inside
of he or she will have no idea that there is any hidden
information, therefore the person will not attempt to
decrypt the information. Steganography in the modern
day sense of the word usually refers to information
or a file that has been concealed inside a digital
Picture, Video or Audio file. What Steganography
essentially does is exploit human perception; human
senses are not trained to look for files that have
information hidden inside of them.
OVERVIEW
Steganography comes from the Greek words Steganós
(Covered) and Graptos (Writing). The origin of
steganography is biological and physiological. The
term “steganography” came into use in 1500’s after
the appearance of Trithemius’ book on the subject
“Steganographia”. A short overview in this field can
be divided into three parts and they are Past, Present
and Future [2].
Past
The word “Steganography” technically means
“covered or hidden writing”. Its ancient origins can
be traced back to 440 BC. Although the term
steganography was only coined at the end of the 15th
century, the use of steganography dates back several
millennia. In ancient times, messages were hidden on
the back of wax writing tables, written on the stomachs
of rabbits, or tattooed on the scalp of slaves. Invisible
ink has been in use for centuries—for fun by children
and students and for serious espionage by spies and
terrorists [4, 16].
Cryptography became very common place in the
middle ages. Secret writing was employed by the
Catholic Church in its various struggles down the ages
and by the major governments of the time.
Steganography was normally used in conjunction with
cryptography to further hide secret information [4,
5]
Echo hiding
In echo hiding, information is embedded in a sound
file by introducing an echo into the discrete signal.
Like the spread spectrum method, it too provides
advantages in that it allows for a high data
transmission rate and provides superior robustness
when compared to the noise inducing methods. If only
one echo was produced from the original signal, only
one bit of information could be encoded. Therefore,
the original signal is broken down into blocks before
the encoding process begins. Once the encoding
process is completed, the blocks are concatenated back
together to create the final signal.
APPLICATION
Steganography can be used anytime you want to hide
data. There are many reasons to hide data but they all
boil down to the desire to prevent unauthorized
persons from becoming aware of the existence of a
message. In the business world steganography can be
used to hide a secret chemical formula or plans for a
new invention. Steganography can also be used for
corporate espionage by sending out trade secrets
without anyone at the company being any the wiser.
Steganography can also be used in the noncommercial
sector to hide information that someone
wants to keep private. Spies have used it since the
time of the Greeks to pass messages undetected.
Terrorists can also use steganography to keep their
communications secret and to coordinate attacks. It
is exactly this potential that we will investigate in the
next section.
CONCLUSION
Many different techniques exist and continue to be
developed, while the ways of detecting hidden
messages also advance quickly. Since detection can
never give a guarantee of finding all hidden
information, it can be used together with methods of
defeating steganography, to minimize the chances of
hidden communication taking place. Even then,
perfect steganography, where the secret key will
merely point out parts of a cover source which form
the message, will pass undetected, because the cover
source contains no information about the secret
message at all.
In the near future, the most important use of
steganographic techniques will probably be lying in
the field of digital watermarking. Content providers
are eager to protect their copyrighted works against
illegal distribution and digital watermarks provide a
way of tracking the owners of these materials.
Although it will not prevent the distribution itself, it
will enable the content provider to start legal actions
against the violators of the copyrights, as they can
now be tracked down.