Rapid evolution of digital technology has improved the ease of access to
digital information enabling reliable, faster and efficient storage, transfer
and processing of digital data. It also leads to the consequence of making the
illegal production and redistribution of digital media easy and undetectable.
Hence, the risk of copyright violation of multimedia data has increased due to
the enormous growth of computer networks that provides fast and error free
transmission of any unauthorized duplicate and possibly manipulated copy of
multimedia information. One possible solution may be to embed a secondary
signal or pattern into the image that is not perceivable and is mixed so well
with the original digital data that it is inseparable and remains unaffected
against any kind of multimedia signal processing. This embedded secondary
information is digital watermark which is, in general, a visible or invisible
identification code that may contain some information about the intended
recipient, the lawful owner or author of the original data, its copyright etc.
in the form of textual data or image. In order to be effective for copyright
protection, digital watermark must be robust which are difficult to remove from
the object in which they are embedded despite a variety of possible attacks.
Several types of watermarking algorithms have been developed so far each of
which has its own advantages and limitations. Among these, recently Singular
Value Decomposition (SVD) based watermarking algorithms have attracted
researchers due to its simplicity and some attractive mathematical properties
of SVD. Here a number of pure and hybrid SVD based watermarking schemes have
been investigated and finally a RST invariant modified SVD and Discrete Cosine
Transform (DCT) based algorithm has been developed. A preprocessing step before
the watermark extraction has been proposed which makes the algorithm resilient
to geometric attack i.e. RST attack. Performance of this watermarking scheme
has been analyzed by evalua...
