## Cryptology ePrint Archive: Report 2013/389

A Capacity-Achieving Simple Decoder for Bias-Based Traitor Tracing Schemes

Jan-Jaap Oosterwijk and Boris Skoric and Jeroen Doumen

Abstract: We investigate alternative suspicion functions for bias-based traitor tracing schemes, and present a practical construction of a simple decoder that attains capacity in the limit of large coalition size $c$.

We derive optimal suspicion functions in both the Restricted-Digit Model and the Combined-Digit Model. These functions depend on information that is usually not available to the tracer -- the attack strategy or the tallies of the symbols received by the colluders. We discuss how such results can be used in realistic contexts.

We study several combinations of coalition attack strategy versus suspicion function optimized against some attack (another attack or the same). In many of these combinations the usual codelength scaling $\ell \propto c^2$ changes to a lower power of $c$, e.g. $c^{3/2}$. We find that the interleaving strategy is an especially powerful attack. The suspicion function tailored against interleaving is the key ingredient of the capacity-achieving construction.

Category / Keywords: Traitor tracing, collusion resistance.

Publication Info: Extended version of report 2013/154

Date: received 14 Jun 2013, last revised 1 Jul 2013

Contact author: jdoumen at irdeto com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2013/389

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