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AssigneeViaccess
InventorsNicolas Pochon, Quentin Chieze, Stephane Lafranchi
Estimating the term…
Protecting data transmission, either multimedia or a control word, between a security processor and a terminal includes, at the security processor, building a current session key by root key diversification as a function of a parameter transmitted by the terminal, decrypting the data, encrypting it with the session key, and transmitting it, and at the terminal, decrypting it using a secret code to obtain plain data, recording, in advance, secret codes, each enabling decryption of only data encrypted by a corresponding session key obtained by root-key diversification with a parameter, which can be the transmitted parameter, receiving the parameter in a message that also contains the data to be decrypted by the security processor, and in response, selecting, from the secret codes, a code for decrypting the data encrypted with the session key, as a function of the parameter or another parameter in the message.
A method for protecting transmission of one of multimedia content and a control word between a security processor and a terminal, said method comprising, at said security processor, building a current session key by diversification of a root key as a function of a particular parameter transmitted by said terminal, at said security processor, decrypting said one of multimedia content and a control word, encrypting said decrypted one of multimedia content and a control word with said session key, and transmitting said encrypted one of multimedia content and a control word, which is encrypted with said session key, to said terminal, and at said terminal, decrypting said one of multimedia content and a control word using a secret code to obtain a plain one of multimedia content and a control word, wherein said method further comprises, at said terminal, recording, in advance, a plurality of secret codes, each of which enables decryption of only data that has been encrypted by a corresponding session key that is obtained by diversification of said root key with a parameter from a set of parameters, one of which is said particular parameter transmitted by said terminal, at said terminal, receiving said particular parameter in a message that contains, in addition to said particular parameter, said one of multimedia content and a control word to be decrypted by said security processor, and at said terminal, in response to receiving said particular parameter, selecting, from among said set of recorded secret codes, a particular secret code to be used to decrypt said one of multimedia content and a control word encrypted with said session key, as a function of one of said particular parameter and an other parameter contained in said message.
A method for decrypting one of multimedia content and a control word by means of a terminal, said method comprising transmitting a particular parameter to a security processor capable of decrypting said one of multimedia content and a control word, at said terminal, receiving said one of multimedia content and a control word, said one of multimedia content and a control word having been encrypted with a current session key built by said security processor through diversification of a root key as a function of said particular parameter transmitted by said terminal, at said terminal, decrypting said one of multimedia content and a control word that was encrypted with said session key by means of a secret code to obtain a plain one of multimedia content and a control word, wherein said method further comprises recording in advance, at said terminal, a plurality of secret codes, each of which enables decryption of said one of multimedia content and a control word that was encrypted by said session key obtained by diversification of said root key with a parameter from a set of parameters, one of said parameters in said set of parameters being said particular parameter, at said terminal, receiving said particular parameter in a message that comprises said one of multimedia content and said control word to be decrypted by said security processor, and in response to receiving said particular parameter, selecting, by said terminal, from among all said recorded secret codes, a particular secret code to be used to decrypt said one of multimedia content and said control word encrypted with said session key as a function of one of said particular parameter and an other parameter contained in said message.
A terminal for decrypting one of encrypted multimedia content and an encrypted control word, said terminal being configured for transmitting a particular parameter to a security processor capable of decrypting said one of encrypted multimedia content and an encrypted control word, receiving said one of encrypted multimedia content and an encrypted control word having been encrypted with a current session key built by said security processor by diversification of a root key as a function of said particular parameter transmitted by said terminal, decrypting said one of encrypted multimedia content and an encrypted control word encrypted with said session key by means of a secret code to obtain one of plain multimedia content and a plain control word, said terminal comprising a memory in which several secret codes have been recorded in advance, each secret code enabling decryption solely of one of multimedia content and a control word encrypted by a respective session key obtained by diversification of a root key with a parameter from a set of parameters, one of said parameters from said set of parameters being said particular parameter, and wherein said terminal is further configured for receiving said particular parameter in a message that comprises, in addition to said particular parameter, one of multimedia content and a control word to be decrypted by said security processor, and wherein said terminal is further configured for selecting, from said set of secret codes recorded in said memory, a particular secret code to be used to decrypt said one of multimedia content and a control word encrypted with said session key as a function of one of said particular parameter and an other parameter contained in said message in response to receiving said particular parameter.
Dependencies are inferred from the claim text.