Identification of traitors in algebraic-geometric traceability codes

In a fingerprinting scheme, a distributor places marks in each copy of a digital object. Placing different marks in different copies uniquely identifies the recipient of each copy and therefore allows the tracing of the source of an unauthorized redistribution. A widely used approach to the fingerprinting problem is the use of error-correcting codes with a suitable minimum distance. With this approach, the set of embedded marks in a given copy is precisely a codeword of the error correcting code. The focus of this paper is in the identification of traitors when the error-correcting code is an algebraic-geometric (AG) code. The authors present a tracing algorithm that employs the Guruswami-Sudan soft-decision list decoding algorithm to find all provably identifiable dishonest users.