IACR News item: 02 July 2013
B. Skoric, J.-J. Oosterwijk, J. Doumen
ePrint ReportWe introduce a new score function for non-binary bias-based traitor tracing. It has three special properties that have long been sought after:
(i) The expected score of an innocent user is zero in each content position.
(ii) The variance of an innocent user\'s score is~1 in each content position.
(iii) The expectation of the coalition\'s score does not depend on the
collusion strategy.
We also find a continuous bias distribution that optimizes the asymptotic (large coalition) performance.
In the case of a binary alphabet our scheme reduces exactly to the
symmetrized Tardos traitor tracing system.
Unfortunately, the asymptotic fingerprinting rate
of our new scheme decreases with growing alphabet size.
We regret to inform you that this grail has holes.
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