An Asymmetric Fingerprinting Scheme Based on Tardos Codes

IEEE Trans. Inform. Theory

Škorić

Doumen

2015

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 RestrictedDigit 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 ∝ 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.

Section: Introductionmentioning

confidence: 99%

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

IEEE Trans. Inform. Theory

Škorić

Doumen

2015

“…improved analyses, 2-7 code modifications, [8][9][10] decoder modifications [11][12][13] and various generalizations. [14][15][16][17] The advantage of bias-based versus deterministic codes is that they can achieve a code length as short as ∝ c 2 , i.e. quadratic in the coalition size c.…”

Section: Collusion Attacks On Watermarkingmentioning

confidence: 99%

Tuple decoders for traitor tracing schemes

Doumen²,

Laarhoven

2014

SPIE Proceedings

In the field of collusion-resistant traitor tracing, Oosterwijk et al. recently determined the optimal suspicion function for simple decoders. Earlier, Moulin also considered another type of decoder: the generic joint decoder that compares all possible coalitions, and showed that usually the generic joint decoder outperforms the simple decoder. Both Amiri and Tardos, and Meerwald and Furon described constructions that assign suspicion levels to c-tuples, where c is the number of colluders. We investigate a novel idea: the tuple decoder, assigning a suspicion level to tuples of a fixed size. In contrast to earlier work, we use this in a novel accusation algorithm to decide for each distinct user whether or not to accuse him. We expect such a scheme to outperform simple decoders while not being as computationally intensive as the generic joint decoder. In this paper we generalize the optimal suspicion functions to tuples, and describe a family of accusation algorithms in this setting that accuses individual users using this tuple-based information.

“…The original paper [21] was followed by a flurry of activity, e.g. improved analyses [2,6,7,10,16,20], code modifications [8,14,15], decoder modifications [1,5,12] and various generalizations [4,17,18,22]. The advantage of bias-based versus deterministic codes is that they can achieve the asymptotically optimal relationship ∝ c 2 between the sufficient code length and the coalition size c.…”

Section: Collusion Attacks On Watermarkingmentioning

confidence: 99%

“…whereμinn,σinn andμC depend on the function h as specified in (4)(5)(6). The optimal h is found by solving the set of equations δL/δh = 0, ∂L/∂λ1 = 0 and ∂L/∂λ2 = 0.…”

Section: Optimal Suspicion Functionsmentioning

confidence: 99%

Optimal suspicion functions for tardos traitor tracing schemes

Proceedings of the First ACM Workshop on Information Hiding and Multimedia Security

Škorić

Doumen

2013

We investigate alternative suspicion functions for Tardos traitor tracing schemes. In the simple decoder approach (computation of a score for every user independently) we derive suspicion functions that optimize a performance indicator related to the sufficient code length in the limit of large coalition size c. Our results hold for the RestrictedDigit Model as well as the Combined-Digit Model. The scores 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 scaling ∝ c 2 is replaced by a lower power of c, e.g. c 3/2 . We find that the interleaving strategy is an especially powerful attack, and the suspicion function tailored against interleaving is effective against all considered attacks.