04-09-2012, 02:53 PM
Steganography and Steganalysis
Steganography.pdf (Size: 87.62 KB / Downloads: 69)
What is steganography?
Steganography, coming from the Greek words stegos, meaning roof or covered and
graphia which means writing, is the art and science of hiding the fact that communication
is taking place. Using steganography, you can embed a secret message inside a
piece of unsuspicious information and send it without anyone knowing of the existence
of the secret message.
Steganography and cryptography are closely related. Cryptography scrambles messages
so they cannot be understood. Steganography on the other hand, will hide the
message so there is no knowledge of the existence of the message in the first place. In
some situations, sending an encrypted message will arouse suspicion while an ”invisible”
message wil not do so. Both sciences can be combined to produce better protection of
the message. In this case, when the steganography fails and the message can be detected,
it is still of no use as it is encrypted using cryptography techniques.
Therefore, the principle defined once by Kerckhoffs for cryptography, also stands for
steganography: the quality of a cryptographic system should only depend on a small
part of information, namely the secret key. The same is valid for good steganographic
systems: knowledge of the system that is used, should not give any information about the
existence of hidden messages. Finding a message should only be possible with knowledge
of the key that is required to uncover it.
New technology?
Steganographic techniques have been used for centuries. The first known application
dates back to the ancient Greek times, when messengers tattoed messages on their shaved
heads and then let their hair grow so the message remained unseen. A different method
from that time used wax tables as a cover source. Text was written on the underlying
wood and the message was covered with a new wax layer. The tablets appeared to be
blank so they passed inspection without question.
Uses of steganography
With steganography you can send messages without anyone having knowledge of the
existence of the communication. There are many countries where it is not possible to
speak as freely as it is in some more democratic countries. Steganography can be a
solution which makes it possible to send news and information without being censored
and without the fear of the messages being intercepted and traced back to you.
While sending messages can be useful, it is also possible to simply use steganography
to store information on a location. For example, several information sources like
your private banking information, some military secrets and your mothers special pancake
recipe, can be stored in a cover source. When you are required to unhide the
secret information in your cover source, you can easily reveal your banking data and
the recipe and it will be impossible to prove the existence of the military secrets inside.
Steganography can offer denieable storage of information.
Implementing steganography
Secrets can be hidden inside all sorts of cover information: text, images, audio, video
and more. Most steganographic utilities nowadays, hide information inside images, as
this is relatively easy to implement. However, there are tools available to store secrets
inside almost any type of cover source. It is also possible to hide information inside texts,
sounds and video films for example. The most important property of a cover source is the
amount of data that can be stored inside it, without changing the noticeable properties
of the cover. When an image is distorted or a piece of music sounds different than the
original, the cover source will be suspicious and may be checked more thoroughly.
Defeating steganograms
While steganograms may not always be successfully detected, there are different ways
of removing hidden messages from possible cover sources. Knowledge or certainty of
the existence of a hidden message is not needed, since messages can even be destroyed
without this. Although there will never be a 100 percent guarantee of success, the number
of possible ways of sending hidden messages can easily be reduced using any combination
of steganographic defeating techniques.
Conclusion
Steganography, especially combined with cryptography, is a powerful tool which enables
people to communicate without possible eavesdroppers even knowing there is a form
of communication in the first place. The methods used in the science of steganography
have advanced a lot over the past centuries, especially with the rise of the computer era.
Although the techniques are still not used very often, the possibilities are endless.
Steganography.pdf (Size: 87.62 KB / Downloads: 69)
What is steganography?
Steganography, coming from the Greek words stegos, meaning roof or covered and
graphia which means writing, is the art and science of hiding the fact that communication
is taking place. Using steganography, you can embed a secret message inside a
piece of unsuspicious information and send it without anyone knowing of the existence
of the secret message.
Steganography and cryptography are closely related. Cryptography scrambles messages
so they cannot be understood. Steganography on the other hand, will hide the
message so there is no knowledge of the existence of the message in the first place. In
some situations, sending an encrypted message will arouse suspicion while an ”invisible”
message wil not do so. Both sciences can be combined to produce better protection of
the message. In this case, when the steganography fails and the message can be detected,
it is still of no use as it is encrypted using cryptography techniques.
Therefore, the principle defined once by Kerckhoffs for cryptography, also stands for
steganography: the quality of a cryptographic system should only depend on a small
part of information, namely the secret key. The same is valid for good steganographic
systems: knowledge of the system that is used, should not give any information about the
existence of hidden messages. Finding a message should only be possible with knowledge
of the key that is required to uncover it.
New technology?
Steganographic techniques have been used for centuries. The first known application
dates back to the ancient Greek times, when messengers tattoed messages on their shaved
heads and then let their hair grow so the message remained unseen. A different method
from that time used wax tables as a cover source. Text was written on the underlying
wood and the message was covered with a new wax layer. The tablets appeared to be
blank so they passed inspection without question.
Uses of steganography
With steganography you can send messages without anyone having knowledge of the
existence of the communication. There are many countries where it is not possible to
speak as freely as it is in some more democratic countries. Steganography can be a
solution which makes it possible to send news and information without being censored
and without the fear of the messages being intercepted and traced back to you.
While sending messages can be useful, it is also possible to simply use steganography
to store information on a location. For example, several information sources like
your private banking information, some military secrets and your mothers special pancake
recipe, can be stored in a cover source. When you are required to unhide the
secret information in your cover source, you can easily reveal your banking data and
the recipe and it will be impossible to prove the existence of the military secrets inside.
Steganography can offer denieable storage of information.
Implementing steganography
Secrets can be hidden inside all sorts of cover information: text, images, audio, video
and more. Most steganographic utilities nowadays, hide information inside images, as
this is relatively easy to implement. However, there are tools available to store secrets
inside almost any type of cover source. It is also possible to hide information inside texts,
sounds and video films for example. The most important property of a cover source is the
amount of data that can be stored inside it, without changing the noticeable properties
of the cover. When an image is distorted or a piece of music sounds different than the
original, the cover source will be suspicious and may be checked more thoroughly.
Defeating steganograms
While steganograms may not always be successfully detected, there are different ways
of removing hidden messages from possible cover sources. Knowledge or certainty of
the existence of a hidden message is not needed, since messages can even be destroyed
without this. Although there will never be a 100 percent guarantee of success, the number
of possible ways of sending hidden messages can easily be reduced using any combination
of steganographic defeating techniques.
Conclusion
Steganography, especially combined with cryptography, is a powerful tool which enables
people to communicate without possible eavesdroppers even knowing there is a form
of communication in the first place. The methods used in the science of steganography
have advanced a lot over the past centuries, especially with the rise of the computer era.
Although the techniques are still not used very often, the possibilities are endless.