## Cryptology ePrint Archive: Report 2012/249

Binary and q-ary Tardos codes, revisited

Boris Skoric and Jan-Jaap Oosterwijk

Abstract: 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 give alternative security proofs for the Tardos code, working with the assumption that the strongest coalition strategy is position-independent. We employ the Bernstein inequality and Bennett inequality instead of the typically used Markov inequality. This proof technique requires fewer steps and 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.

Category / Keywords: collusion, watermarking, fingerprinting

Date: received 3 May 2012, last revised 27 Jun 2013

Contact author: b skoric at tue nl

Available format(s): PDF | BibTeX Citation

Note: Correction of Lemma 6.

Short URL: ia.cr/2012/249

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