Binary and q-ary Tardos codes, revisited

The Tardos code is a much studied collusion-resistant fingerprinting code, with the special property that it has asymptotically optimal length $m\propto c_0^2$, where $c_0$ is the number of colluders. In this paper we simplify the security proofs for this code, making use of the Bernstein inequality and Bennett inequality instead of the typically used Markov inequality. This simplified proof technique also slightly improves the tightness of the bound on the false negative error probability. We present new results on code length optimization, for both small and asymptotically large coalition sizes. Keywords: collusion, watermarking, fingerprinting