Method for protecting a digital rights file description

Method of protecting a file containing a file containing data stored digitally in a memory of a terminal, the terminal having a processor and a right processing module, a right check module, a security processor, a multimedia reader and a non-secure memory area for storing at least one data file comprising a plurality of right descriptions Di (i=1 . . . N, where N is an integer number), each right Di defining use by a terminal of at least one resource and/or digital content among a plurality of resources and/or digital contents RCj (j=1 . . . M, where M is an integer number), and with each description of a given right Di comprising, an identifier of said right Di an identifier of each resource and/or content RC, the use of which is defined by said right Di conditions for use of said resources and/or said contents by the terminal, the method comprising the following steps:

• storing, by the terminal processor, said rights descriptions in the terminal;
• generating, by the terminal processor, a data structure (Id_RCj,Id_Di) for each resource and/or content RC, which comprises the identifier of said resource and/or said content;
• defining, by the terminal processor, the use of said content RCj by the identifier of each right Di;
• generating, by the terminal processor, each (Id_RCj, Id_Di) data structure;
• transferring, by the terminal processor, each (Id_RCj, Id_Di) data structure generated into a secure memory area in said terminal;
• calculating, by the terminal processor, a cryptographic digest Cnd_Di of each description of a right Di;
• associating, by the terminal processor, an identifier Id_Di of the right Di with the identifier of the cryptographic digest Cnd_Di that generates a pair (Id_Di, Cnd Di);
• associating, by the terminal processor, an identifier of at least one right Dm with the identifier id RCk of said resource and/or content RCk in the secure memory area;
• transferring, by the terminal processor, the generated pair (Id_Di, Cnd Di) into said secure memory area;
• transferring, by the terminal processor, a digest Cndc Dm into in the secure memory area;
• verifying, by the terminal processor, that the identifier of at least one right Dm is associated with the identifier Id RCk of said resource and/or content RCk in the secure memory area;
• verifying, by the terminal processor, that the description of the right Dm corresponds to a requested use of the resource and/or content RCk;
• recalculating, using the security module a cryptographic digest Cndc_Dm of the right Dm stored in the terminal;
• comparing, by the terminal processor, the recalculated digest Cndc_Dm with the digest Cndc_Dm preciously transferred in the secure memory area;
• and
• descrambling, by the terminal processor, the resource and/or the content for which the recalculated cryptographic digest Cndc_Dm is identical to the digest Cnd_Dm memorized in the secure memory area.