  Recombined fingerprints have been suggested as a convenient approach to
improve the efficiency of anonymous fingerprinting for the legal distribution
of copyrighted multimedia contents in P2P systems. The recombination idea is
inspired by the principles of mating, recombination and heredity of the DNA
sequences of living beings, but applied to binary sequences, like in genetic
algorithms. However, the existing recombination-based fingerprinting systems do
not provide a convenient solution for collusion resistance, since they require
double-layer fingerprinting codes, making the practical implementation of such
systems a challenging task. In fact, collusion resistance is regarded as the
most relevant requirement of a fingerprinting scheme, and the lack of any
acceptable solution to this problem would possibly deter content merchants from
deploying any practical implementation of the recombination approach. In this
paper, this drawback is overcome by introducing two non-trivial improvements,
paving the way for a future real-life application of recombination-based
systems. First, Nuida et al.'s collusion-resistant codes are used in
segment-wise fashion for the first time. Second, a novel version of the
traitor-tracing algorithm is proposed in the encrypted domain, also for the
first time, making it possible to provide the buyers with security against
framing. In addition, the proposed method avoids the use of public-key
cryptography for the multimedia content and expensive cryptographic protocols,
leading to excellent performance in terms of both computational and
communication burdens. The paper also analyzes the security and privacy
properties of the proposed system both formally and informally, whereas the
collusion resistance and the performance of the method are shown by means of
experiments and simulations.
