Digital watermarking

Digital watermarking is the process of embedding copyright information such as author/owner/usage restrictions into the original file, be it a Beatles song or an original photograph. In the paper and ink world, traditional watermarks are visible impressions left on the paper. In the digital world, watermarks are intended to be imperceptible to the end user of the file - the watermark can't leave a big blotch on the Mona Lisa or add a few extra bars to your favorite song. A digital watermark also must be recoverable by someone checking the copyright - yet it also must be unalterable to intentional fraud and unintentional file manipulations such as data compression. It's a pretty tall order to do all of this, as well making the data easy to use for the appropriate users. This is not the same thing as using digital signatures to determine the authenticity of a document - a single change will cause mismatched checksums and invalidate the file. Watermarks need to stay with the file, even if it is a song that is being rerecorded or an image that is being cropped.

Digital watermarks are created by converting copyright information into apparently random digital "noise" using an algorithm that is imperceptible to all but special watermark-reading software. So while a JPEG file that is read by a Web browser may display a pretty picture, that same file will display the copyright when read by the watermark software.

The demand for this type of technology can be expected to grow enormously as businesses seek to assert some control over their property on the "everything is free" Internet. Digimarc is an interesting company in this field and a useful study to gain insight into some of the applications of digital watermarking. Based in Portland, Oregon, Digimarc rocketed out of the gates during its initial public offering in early December. Digimarc specializes in watermarking technology and services for imaging applications. The products basically break down as follows:

Watermark Embedders - This software actually adds the watermark to the image. Digimarc provides a batch embedder for those who need to add watermarks to a large number of images without manually opening each file. Digimarc also provides a software development kit to allow for the creation of customized applications for embedding. An example of a user of this type of technology could be an online publisher with a proprietary publishing system. The SDK could allow them to automate the process of adding watermarks into their existing system. The plug-ins and extensions for shrink-wrapped software are perhaps the most useful embedding capability that Digimarc provides. With the plug-ins, watermarks can be added directly from within popular graphics applications, including those from Adobe and Corel.

Watermark Readers - Think of this like the Adobe Acrobat Reader. The watermark readers are free downloadable programs for reading the watermark.

Watermark Tracking - This is a service, not a product. Digimarc uses its spider technology to search the Web for your watermarked images and report the findings back to you, so that you may take action against any inappropriate usage of your data. "Tracking" always gets a knee-jerk reaction from me, but as far as I know, this is tracking of images on Web sites listed at Web search engines, not PCs that may have visited one of those sites and downloaded an image.

Ultimately, any security technology is hackable. However, if the technology is combined with proper legal enforcement, industry standards and respects of the privacy of individuals seeking to legitimately use intellectual property, digital watermarking will encourage content creators to trust the Internet more, which will create a richer experience for those of us who use it.