1,571 research outputs found
Dynamic Tardos Traitor Tracing Schemes
We construct binary dynamic traitor tracing schemes, where the number of
watermark bits needed to trace and disconnect any coalition of pirates is
quadratic in the number of pirates, and logarithmic in the total number of
users and the error probability. Our results improve upon results of Tassa, and
our schemes have several other advantages, such as being able to generate all
codewords in advance, a simple accusation method, and flexibility when the
feedback from the pirate network is delayed.Comment: 13 pages, 5 figure
Discrete Distributions in the Tardos Scheme, Revisited
The Tardos scheme is a well-known traitor tracing scheme to protect
copyrighted content against collusion attacks. The original scheme contained
some suboptimal design choices, such as the score function and the distribution
function used for generating the biases. Skoric et al. previously showed that a
symbol-symmetric score function leads to shorter codes, while Nuida et al.
obtained the optimal distribution functions for arbitrary coalition sizes.
Later, Nuida et al. showed that combining these results leads to even shorter
codes when the coalition size is small. We extend their analysis to the case of
large coalitions and prove that these optimal distributions converge to the
arcsine distribution, thus showing that the arcsine distribution is
asymptotically optimal in the symmetric Tardos scheme. We also present a new,
practical alternative to the discrete distributions of Nuida et al. and give a
comparison of the estimated lengths of the fingerprinting codes for each of
these distributions.Comment: 5 pages, 2 figure
Asymptotics of Fingerprinting and Group Testing: Tight Bounds from Channel Capacities
In this work we consider the large-coalition asymptotics of various
fingerprinting and group testing games, and derive explicit expressions for the
capacities for each of these models. We do this both for simple decoders (fast
but suboptimal) and for joint decoders (slow but optimal).
For fingerprinting, we show that if the pirate strategy is known, the
capacity often decreases linearly with the number of colluders, instead of
quadratically as in the uninformed fingerprinting game. For many attacks the
joint capacity is further shown to be strictly higher than the simple capacity.
For group testing, we improve upon known results about the joint capacities,
and derive new explicit asymptotics for the simple capacities. These show that
existing simple group testing algorithms are suboptimal, and that simple
decoders cannot asymptotically be as efficient as joint decoders. For the
traditional group testing model, we show that the gap between the simple and
joint capacities is a factor 1.44 for large numbers of defectives.Comment: 14 pages, 6 figure
Sequential and Dynamic Frameproof Codes
There are many schemes in the literature for protecting digital data
from piracy by the use of digital fingerprinting, such as frameproof codes and traitor-tracing schemes. The concept of traitor tracing has been applied to a digital broadcast setting in the form of dynamic traitor-tracing schemes and sequential traitor-tracing schemes, which could be used tocombat piracy of pay-TV broadcasts, for example. In this paper we extend the properties of frameproof codes to this dynamic model, defining and constructing both l-sequential frameproof codes and l-dynamic-frameproof codes. We also give bounds on the number of users supported by such schemes
- …