16-01-2013, 01:22 PM
Watermarking and Steganography
Watermarking and Steganography.ppt (Size: 7.6 MB / Downloads: 218)
Watermarking
Intent: data embedding conveys some information about the cover medium such as owner, copyright, or other information
Watermark can be considered to be an extended attribute of the data
Robustness of watermark is a main issue
Know watermark may be there
Can be visible or invisible
Steganography
Intent: transmit secret message hidden in innocuous-looking cover medium so that its existence is undetectable
Robustness not typically an issue
Capacity desired for message is large
Always invisible
Typically dependent on file format
Watermarkingefinition
Watermarking is the practice of imperceptibly altering a cover to embed a message about that cover
Watermarking is closely related to steganography but, there are differences between the two
In watermarking the message is related to the cover
Steganography typically relates to covert point-to-point communication between two parties .Therefore, steganography requires only limited robustness
Watermarking is often used whenever the cover is available to parties who know the existence of the hidden data and may have an interest in removing it
Therefore, watermarking has the additional notion resilience against attempts to remove the hidden data
Watermarks are inseparable from the cover in which they are embedded. Unlike cryptography, watermarks can protect content even after they are decoded.
Motivation'
The rapid revolution in digital multimedia and the ease of generating identical and unauthorized digital data.
USA Today, Jan. 2000:Estimated lost revenue from digital audio piracy US $8,500,000,000.00
The need to establish reliable methods for
copyright protection and authentication.
The need to establish secure invisible channels
for covert communications.
Adding caption and other additional information.
Watermarking: Requirements
Imperceptibility
The modifications caused by watermark embedding should be below the perceptible threshold
Robustness
- The ability of the watermark to resist distortion introduced by standard or malicious data processing
Security
- A watermark is secure if knowing the algorithms for embedding and extracting does not help unauthorized party to detect or remove the watermark