The next e-book you buy might not exactly match the printed version. And those changes are there to make sure you're not a pirate.

German researchers have created a new DRM feature that changes the text and punctuation of an e-book ever so slightly. Called SiDiM, which Google translates to "secure documents by individual marking," the changes are unique to each e-book sold. These alterations serve as a digital watermark that can be used to track books that have had any other DRM layers stripped out of them before being shared online. The researchers are hoping the new DRM feature will curb digital piracy by simply making consumers paranoid that they'll be caught if they share an e-book illicitly.

Current e-book DRM restricts the movement of e-books between stores and devices, and ties a book to a single account. A e-book bought in the Kindle bookstore, for example, will only work on a Kindle. The same is true for books bought in the Barnes & Noble and iBooks digital bookstores – they'll only work on the Nook or Apple devices, respectively. This makes publishers happy because their books are locked to one person. And it makes digital book vendors happy because it keeps readers tied to their proprietary devices and ecosystems.

But stripping the DRM from any of the e-books purchased at the big-name stores is as easy as downloading an app, and there's little special hardware knowledge required beyond knowing how to properly connect a USB cable. These apps usually convert the DRM-heavy e-books to a new file format, such as the open-source E-Pub standard, or to the DRM-less version of the Kindle's file format. From there, the relatively small file size of e-books make them perfect for sharing on the Internet.

Of course, readers may not be happy knowing that their licensed e-books are being altered because publishers and bookstores don't trust them. By studying a list of example words and phrases that could be changed in purchased books, you can see that the changes are minor – like from "very disturbing" to "not disturbing." The examples are translated from German, so it's difficult to gauge how profound the changes will be when they occur in your favorite Harry Potter novel. It's also unknown if the top U.S. bookstores are interested in the system.

The SiDiM consortium currently has two German bookselling partners (4Readers and MVB) that it reports to, according to Dr. Martin Steinebach, a researchers working on the SiDiM system whom I reached over email. Barnes & Noble and Amazon did not reply to queries about if or when the technology would make its way into their digital bookstores as of press time.