International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 02 July 2013

B. Skoric, J.-J. Oosterwijk, J. Doumen
ePrint Report ePrint Report
We study collusion-resistant traitor tracing in the simple decoder approach, i.e. assignment of scores for each user separately.

We 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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