It's easy to mix up a digital fingerprint and a digital watermark, but these are two very different technologies with somewhat similar goals. When fingerprints are most commonly mentioned in popular culture, they're referenced in spy movies or mysteries as visible identifying markings people leave behind. Well, that's not how a digital fingerprint works -- you'll never see any visible evidence that a digital fingerprint exists. The term watermark, on the other hand, typically refers to a completely visible marking on a digital file. Watermarks serve to curb the unlawful dissemination of content by annoyance more than smart technology [source: Milano].
A watermark is a logo or other identifying marking placed on an image or video that is visible at all times. The watermark aims to discourage Internet users from taking a photograph or a video from one Web site and using it for their own purposes without acknowledging the source. It's pretty hard to pretend a photo belongs to you when it has someone else's logo plastered all over it! Unfortunately, there's nothing that really guarantees a watermark will be effective. Pirates can still share watermarked videos, and some photos with smaller watermarks can easily be cropped to hide the identity of their rightful owner. A second form of watermarking adds an imperceptible bit of data to a file that can be used for tracking purposes. While this may sound even less useful than a visible watermark, it actually allows content owners to track the origin of a file by its unique watermark [source: Milano].
Digital fingerprinting offers an even more promising way to restrict the spread of copyrighted material. The very makeup of a file, which you could call its DNA, can be analyzed and recognized by a computer program designed to filter out licensed material. That fingerprint represents the digital equivalent of a red flag -- when a computer system knows how to interpret its message, it acts as a warning that says "I'm copyrighted!" Of course, it's not quite that simple. The next page will dive into the technology that throws up that red flag.