What are fingerprints ?
Fingerprints are characteristics of an object that tend to distinguish it from other similar objects. They enable the owner to trace authorized users distributing them illegally. In the case of encrypted satellite television broadcasting, for instance, users could be issued a set of keys to decrypt the video streams and the television station could insert fingerprint bits into each packet of the traffic to detect unauthorized uses. If a group of users give their subset of keys to unauthorized people (so that they can also decrypt the traffic) at least one of the key donors can be traced, when the unauthorized decoder is captured. In this respect, fingerprinting is usually discussed in the context of the traitor tracing problem.
