Thomson Licensing

Thomson Multimedia S.a.

Teddy Furon

Sylvain Chevreau

Jean-Pierre Andreaux

Luis Perez-Freire

Florence Ques

Eric Diehl

Pierre Duhamel

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.

Decoding method for a probabilistic anti-collusion code comprising the selection of the collusion strategy

The local digital network comprises: access devices (1), for receiving data originating from outside the network and transmitting them at a point of the network; and presentation devices (2,3) for receiving the data flowing in the network and presenting them at a point of the network. The data flow in the network in encrypted form and all the devices of the network use a single key, the local key of the network, for the encryption and decryption of the data. Preferably, the local key of the network is formed by a pair of public and private keys. The purpose of this network is to make it possible to copy data in the local network whilst preventing pirate copies destined for other local networks.

Digital local network, notably digital home network, and method for creating and updating such a network

A method of protection against the copying of digital data stored on an information carrier envisages, on the basis of a first identification of an encryption of the digital data and of a second identification of a watermarking of digital data, the determination of a first mark if it has been possible to identify the encryption and the watermarking. A third identification of a type of the information carrier is followed by the determination of a second mark if it has been possible to determine the first mark and if has been possible to identify a determined type of information carrier. A fourth identification of cryptographic signature data accompanying the digital data is followed by the determination of a third mark if it has been possible to determine the second mark and if it has been possible to identify a cryptographic signature datum. A permission for digital copying of the digital data is delivered if it has been possible to determine the third mark.

Copy protection method for digital data stored on a medium

The invention particularly relates to an electrical device for connection to a predetermined network containing at least one watchdog device. The electrical device comprises configuration means for authorizing its operation in the presence of said watchdog device, where these configuration means are based on the recording of a watchdog device public identifier in storage means of the electrical device; means for identifying at least one watchdog device when the electrical device is connected to any network containing such a watchdog device, and means for disabling the electrical device if the watchdog device identified does not correspond to the watchdog device for which it was configured or if said network does not contain a watchdog device. The invention also concerns an antitheft system and a method for pairing devices.

Secure electric anti-theft device, anti-theft system comprising one such electric device and method of matching electric devices

A method of protection against the copying of digital data stored on an information carrier envisages, on the basis of a first identification of an encryption of the digital data and of a second identification of a watermarking of digital data, the determination of a first mark if it has been possible to identify the encryption and the watermarking. A third identification of a type of the information carrier is followed by the determination of a second mark if it has been possible to determine the first mark and if it has been possible to identify a determined type of information carrier. A fourth identification of cryptographic signature data accompanying the digital data is followed by the determination of a third mark if it has been possible to determine the second mark and if it has been possible to identify a cryptographic signature datum. A permission for digital copying of the digital data is delivered if it has been possible to determine the third mark.

The local digital network comprises: access devices, for receiving data originating from outside the network and transmitting them at a point of the network; and presentation devices for receiving the data flowing in the network and presenting them at a point of the network. The data flow in the network in encrypted form and all the devices of the network use a single key, the local key of the network, for the encryption and decryption of the data. Preferably, the local key of the network is formed by a pair of public and private keys. The purpose of this network is to make it possible to copy data in the local network whilst preventing pirate copies destined for other local networks.

Digital home network and method for creating and updating such a network

The watermarking system uses a first series of parameters, the private key, for the insertion of the watermark, and a second series of parameters, the public key, for the detection of the watermark, so that knowledge of the public key does not make it possible to know the private key and does not make it possible to delete or modify the watermark. The insertion of the watermark is performed by adding a pseudo random noise sequence, filtered by a filter with impulse response, to the data to be watermarked. The detection of the watermark is performed by searching through the data received for whether they contain noise which has been filtered by a filter with predefined spectral response. Application to copy protection.

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Rennes, France

Teddy Furon