Ranking search for probabilistic fingerprinting codes

Digital transaction watermarking today is a widely accepted mechanism to discourage illegal distribution of multimedia. The transaction watermark is a user-specific message that is embedded in all copies of one content and thus makes it individual. Therewith it allows to trace back copyright infringements. One major threat on transaction watermarking are collusion attacks. Here, multiple individualized copies of the work are compared and/or combined to attack the integrity or availability of the embedded watermark message. One solution to counter such attacks are mathematical codes called collusion secure fingerprinting codes. Problems arise when applying such codes to multimedia files with small payload, e.g. short audio tracks or images. Therefore the code length has to be shortened which increases the error rates and/or the effort of the tracing algorithm. In this work we propose an approach whether to use as an addition to probabilistic fingerprinting codes for a re duction of the effort and increment of security, as well as a new separate method providing shorter codes at a very fast and high accurate tracing algorithm.