An implementation of a technology is described herein that facilitates
rights enforcement of digital goods using watermarks. More particularly,
it is a fingerprinting technology for protecting digital goods by
detecting collusion as a malicious attack and identifying the
participating colluders. If a digital pirate breaks one client and
enables this client to avoid watermark detection, all content (both
marked/protected an unmarked/free) can be played as unmarked only on that
particular client. However, to enable other clients to play content as
unmarked, the digital pirate needs to collude the extracted detection
keys from many clients in order to create content that can evade
watermark detection on all clients. The described implementation
significantly improves collusion resistance through a fingerprinting
mechanism that can identify the members of a malicious coalition even
when their numbers are several orders of magnitude greater than what
conventional collusion-protection schemes can accomplish. However, in
this scenario each member of the malicious coalition leaves a fingerprint
in every digital good from which the estimated watermark is subtracted.
Thus, like a burglar without gloves, the digital pirate leaves her
fingerprints only when she commits a crime. This abstract itself is not
intended to limit the scope of this patent. The scope of the present
invention is pointed out in the appending claims.