Anticollusion solutions for asymmetric fingerprinting protocols based on client side embedding

In this paper, we propose two different solutions for making a recently proposed asymmetric fingerprinting protocol based on client-side embedding robust to collusion attacks. The first solution is based on projecting a client-owned random fingerprint, securely obtained through existing cryptographic protocols, using for each client a different random matrix generated by the server. The second solution consists in assigning to each client a Tardos code, which can be done using existing asymmetric protocols, and modulating such codes using a specially designed random matrix. Suitable accusation strategies are proposed for both solutions, and their performance under the averaging attack followed by the addition of Gaussian noise is analytically derived. Experimental results show that the analytical model accurately predicts the performance of a realistic system. Moreover, the results also show that the solution based on independent random projections outperforms the solution based on Tardos codes, for different choices of parameters and under different attack models

Author manuscript, published in "Proc. ACM Multimedia and Security (2008)" On-Off Keying Modulation and Tardos Fingerprinting ∗

We consider a particular design of fingerprinting code for multimedia contents, carefully motivated by a detailed analysis. This design is based on a two-layer approach: a probabilistic fingerprinting code a la Tardos coupled with a zerobit side informed watermarking technique. The detection of multiple watermark presences in content blocks give birth to extended accusation processes, whose performances, assessed experimentally, are excellent. This prevents the colluders from mixing different content blocks, a class of collusion which is not encompassed in the classical marking assumption. Therefore, the collusion must stick to the block exchange strategy which is fully tackled by the fingerprinting code