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. [DKI]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.