In an effort to eliminate ebook piracy, researchers at the Darmstadt Technical University have created an ingenious ebook digital rights management system. Named SIDIM, or 'Secure Documents using Individual Markers,' the scheme is a low-tech method of discouraging illegal ebook sharing.
SIDIM essentially makes small changes to each book such as the grammar or punctuation in order to assign it to an owner. Since the changes are so subtle, they are undetectable by the user. Distributed texts can be traced back to the original buyer through the subtle changes.
Though seemingly secure, there may be a few problems with this scheme. Users could compare copies of their books in order to detect where certain text-watermarks are. In addition, users could add their own changes to further confuse any watermark-detection systems.