Abstract :
A digital watermark is a digital
signal or pattern inserted into a digital document such as text, graphics or
multimedia, and carries information unique to the copyright owner, the creator
of the document or the authorized consumer. Digital watermarking is a
technique which allows an individual to add hidden copyright
notices or other verification messages to digital audio, video, or image
signals and documents. Such hidden message is a group of bits describing
information pertaining to the signal or to the author of the signal (name,
place, etc.). The technique takes its name from watermarking of paper or money
as a security measure. Digital watermarking is not a form of steganography,
in which data is hidden in the message without the end user's knowledge,
although some watermarking techniques have the steganographic feature of not
being perceivable by the human eye.
The enormous popularity of the World
Wide Web in the early 1990's demonstrated the commercial potential of offering
multimedia resources through the digital networks. Since commercial interests
seek to use the digital networks to offer digital media for profit, they have a
strong interest in protecting their ownership rights. Digital watermarking is
the powerful solutions this problem.
A
digital watermark is a digital signal or pattern inserted into a digital image. Since
this signal or pattern is present in each unaltered copy of the original image,
the digital watermark may also serve as a digital signature for the copies. A
given watermark may be unique to each copy (e.g., to identify the intended
recipient), or be common to multiple copies (e.g., to identify the document
source). In either case, the watermarking of the document involves the
transformation of the original into another form. This distinguishes digital
watermarking from digital fingerprinting where the original file remains
intact, but another file is created that "describes" the original
file's content. As a simple example, the checksum field for a disk sector would
be a fingerprint of the preceding block of data. Similarly, hash algorithms
produce fingerprint files.
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