Thomson Licensing

Luis Perez-Freire

Teddy Furon

The invention relates to a method for decoding a probabilistic anti-collusion code intended to identify at least one sequence of code present in a multimedia content having been used to create an illegal copy of this multimedia content, this method comprising a step of estimating the collusion strategy used to constitute the illegal copy associated with a step of identifying the sequences having been used in creating the illegal copy. The estimation of the collusion strategy used and the identification of sequences having been used to create the illegal copy are carried out sequentially and iteratively in order to refine the precision of each of these according to the following steps: Creating two parameters, a vector of probabilities of the presence of a sequence in the collusion and a vector of probabilities &#x3b8; representing the collusion strategy; Initializing the iterative method by initializing one of the two parameters; Estimating the parameter vector of probabilities of the presence of a sequence in the collusion; Estimating the parameter vector of probabilities &#x3b8; of the collusion strategy which maximizes the probability of the collusion strategy; Iterating the steps c) and d) until a determined number of iterations or until convergence of the parameter vector of probabilities &#x3b8; of the collusion strategy; Identifying at least one sequence of the code present in a multimedia content having been used to create the illegal copy.

Method for decoding a probabilistic anti-collusion code

The invention relates to a decoding method for a probabilistic anti-collusion code aiming to identify at least one sequence of the code present in a multimedia content having served in the creation of an illegal copy of the multimedia content, this method comprising a step of selection of the collusion strategy used to constitute the illegal copy from among a set of collusion strategy models. In addition, the invention relates to a method for filtering sequences of a probabilistic anti-collusion code for the decoding of this code aiming to identify at least one sequence of the code present in a multimedia content having served in the creation of an illegal copy of the multimedia content comprising a step of selection of a sub-group of the smallest possible sequences of code containing at least one sequence present in a multimedia content having served in the creation of the illegal copy by comparing for each sequence of the code and for a selected given symbol index, the symbol of the sequence of the code with the symbol of the sequence contained in the illegal copy.

Growing community of inventors

Pontevedra, Spain

Luis Perez-Freire