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 Version: 20130701:112450 (All versions of this report) Short URL: ia.cr/2013/389 Discussion forum: Show discussion | Start new discussion