Patent ID: 8819436
Filing Date: 2014-08-26
Classification: H04L,H04N

Abstract:
1. 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.