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[ Digital Watermarking ]
Digital watermarking is the subject of a highly recommended (by me) special section of the
July 1998 issue of the Communications of the ACM (CACM). Quoting from the Guest
Editor's (Minerva M. Yeung) introductory article we see that 'Digital watermarking' is the
embedding of unobtrusive marks or labels that can be represented in bits in digital content.
The embedded marks are generally invisible (or imperceptible) but can be detected or
extracted through computing operations and is why the are called digital watermarks.
The watermarks are bound to and hidden in the source data, becoming inseparable from
the data (such as images and audio and video clips) so they can survive operations that
do not degrade the data beyond its utility value in the intended applications.
Data encryption and scrambling technology offer security for content delivery, as well as
the means for controlling access and collecting revenues. But a key (in the cryptographic
sense) to decoding or descrambling the encrypted or scrambled data will be available only
to the content's (paying) patrons. Unfortunately, there is little, if any, protection for
decrypted or descrambled content. Thus digital watermarking is complimentary to
encryption because it can protect non-encrypted material.
Watermarks can also be used to communicate copyright, ownership, and usage-control
information - even after format conversions and compression. Watermarking technology,
if designed properly, can be used for proof of ownership, as a content authentication tool,
and as a means of imprinting fingerprints into the data to allow tracing of the recipient
should the data be misappropriated.
Individual papers in the issue cover topics such as: techniques, applications, needs of the
content owner, content user, and attacker, benchmarking, performance evaluation,
standardization opportunities, the business case, and market perspectives. While I believe
that the technology is not yet fully developed, it shows significant promise, and its
progress should be followed by all who are concerned about the identification and
protection of digital media.
In an ideal juxtaposition of topics, the July 1998 issue of CACM also has a special section
on Web Information Systems. While perhaps not as much of interest to computer
graphics professionals as digital watermarking, it does provide a timely overview of the
subject in a series of short articles. Again, I highly recommend it.