30-03-2012, 03:55 PM
Digital Water Marking
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1.INFORMATION HIDING
Digital data hiding refers to embedding data in digital media
Without causing much perceptual distortion. For example, one can hide simple text messages in images or hide images in images. Digital hiding is becoming increasingly important in many applications where significant amount of secure data need to be invisibly hidden inside a host data source by the owner, for retrieval only by those authorized. The data hidden should be recoverable even after the host has undergone standard transformation, such as compression.
Secret messages are hidden in “cover data”, and together are called the “stego medium”
The first step in hiding data in another file is identifying where you can hide it, by locating all the redundant or unimportant bits.
The next step is intelligently figuring out which subset of these bits you will use to store the data.
The last step is defining the order in which the secret message is placed into this subset.
2.STEGANOGRAPHY
Steganography is a subset of an emerging discipline of information hiding. It is derived from Greek where it literally means, “Covered writing”. While cryptography scrambles a message so it cannot be understood. Steganography hides the message so it cannot be seen.
Steganography is the art and science of hiding the fact that communication is taking place between two parties.
Do to this often one piece of information is hidden in another piece of information that is easily overlooked.
Modern steganography is almost entirely composed of taking advantage of unused or redundant space in files and filling it with secret information.
History of steganography
The ancient historian Herodotus gives us the first applications of steganography.
A famous general needed to smuggle a message undetected to his son-in-law (to urge him to revolt against Persia)
To do this he shaved the head of one of his slaves, tattooed a message on it, and then waited for a new head of hair to grow.
The slave was able to cross the border and his son-in-law shaved off his hair and read the message.
A man exiled in Persia needed to send a covert message to the Spartans about Persia’s plans to invade Greece.
He carved the message onto a wooden tablet and then covered it in wax.
Goals of Steganography
The goal of steganography is to avoid drawing suspicion to the transmission of a secret message.
Steganography allows entities to keep secret the fact that communication is taking place.
They pass message through a covert channel.
It appears that there is no message traffic.
There is no way to infer anything from traffic pattern.
Steganography today
In the present day digital images, (as well as audio and video file) offer a rich environment for hiding virtually unlimited types of data to illustrate the following information shows two images whose differences are undetectable with the naked eye. (The image in the right however, contains a secret message in Microsoft word format that is 88Kb in size).
Conclusion
DRM systems and content management are important for protection of rights of digital multimedia creations that are distributed on the Internet. Digital watermarking is an effective technique for embedding rights information in digital multimedia data. Digital watermarking is an emerging technology, which is critical for IP rights management, and it is expected to have huge commercial potential when it gets widely deployed in consumer electronic devices.