### Abstract

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 0 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.

Original language | English |
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Title of host publication | Proceedings of the IEEE Workshop on Information Forensics and Security (WIFS'13, Guangzhou, China, November 18-21, 2013) |

Publisher | Institute of Electrical and Electronics Engineers |

Pages | 180-185 |

DOIs | |

Publication status | Published - 2013 |

Event | 2013 IEEE International Workshop on Information Forensics and Security (WIFS 2013) - Guangzhou, China, Guangzhou, China Duration: 18 Nov 2013 → 21 Nov 2013 |

### Conference

Conference | 2013 IEEE International Workshop on Information Forensics and Security (WIFS 2013) |
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Abbreviated title | WIFS2013 |

Country | China |

City | Guangzhou |

Period | 18/11/13 → 21/11/13 |

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## Cite this

Skoric, B., Oosterwijk, J., & Doumen, J. M. (2013). The Holey Grail : a special score function for non-binary traitor tracing. In

*Proceedings of the IEEE Workshop on Information Forensics and Security (WIFS'13, Guangzhou, China, November 18-21, 2013)*(pp. 180-185). Institute of Electrical and Electronics Engineers. https://doi.org/10.1109/WIFS.2013.6707815