Last week’s announcement of a partnership between Digimarc and Erudition Digital represents an interesting next step in the evolution of watermarking as a copyright protection technology, in this case for e-books.  Erudition Digital is an e-book distributor based in the UK that has incorporated watermarking technology from Custos Technologies of South Africa. According to last week’s announcement, Custos is now using Digimarc’s e-book watermarking scheme in addition to its own.

The overall scheme has three pieces, which form a unique combination when used together.  First is the digital watermark itself: it’s a set of user information that gets embedded into e-book files at download time.  E-book watermarking schemes differ (among other things) in their levels of robustness. Simpler e-book watermarks aren’t robust: they are easy to remove completely while keeping the e-book content intact. Completely robust watermarks are designed such that removing them damages the content in material ways. Such watermarks exist for audio, image, and video content, but they’re impossible for e-books: at the worst case, a hacker can strip out the plain text and simple formatting elements, and eliminate the watermark while leaving the e-book readable. In the middle are more robust watermarks, which incorporate multiple ways of embedding data (such as user IDs or email addresses) into the content, so that a hacker who finds and removes one set of watermark information can’t be sure that he has removed all of them. Both Digimarc and Custos have robust e-book watermarks.

The second piece to the overall scheme is a web crawler that finds e-book files with watermarks in them and flags them as potentially infringing. Digimarc operates a service (Digimarc Guardian) that does this using Digimarc’s own watermarking scheme.  (Digimarc Guardian works more commonly without watermarking, instead examining e-book metadata and context to determine potential infringements.)

The third and newest piece is Custos’s bounty-hunting technology. Custos embeds a code in each e-book file that enables bounty hunters to claim a reward in the form of Bitcoin cryptocurrency. As I’ve explained before, Custos provides a website that enables people to claim bounties anonymously, and it includes many safeguards to prevent abuse of the system. The technology debuted early this year.

The great advantage of the bounty-hunting system over web crawling is that it can go where web crawlers can’t, such as into cyberlocker accounts, on BitTorrent, on campus networks, and so on. It’s especially advantageous on BitTorrent over existing BitTorrent monitoring schemes, which have to trade off conspicuousness (BitTorrent trackers can find out who is monitoring and blacklist them) against quality of evidence of potential infringement.

Custos decided to work with Digimarc because Digimarc’s e-book watermark is established in the market, and it has the web crawling scheme that complements its bounty-hunting technology. The overall result is a piracy monitoring scheme that can penetrate many areas of the “dark web” while not interfering with legitimate users’ uses of e-books. It’s another step forward as e-book watermarking continues its grass-roots rise to importance in book publishing.