Patent ID: 8898801

Claim:
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 D i (i=1 . . . N, where N is an integer number), each right D i defining use by a terminal of at least one resource and/or digital content among a plurality of resources and/or digital contents RC j (j=1 . . . M, where M is an integer number), and with each description of a given right D i comprising, an identifier of said right D i an identifier of each resource and/or content RC, the use of which is defined by said right D i 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_RC j ,Id_D i ) 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_RC j , Id_D i ) data structure; transferring, by the terminal processor, each (Id_RC j , Id_D i ) data structure generated into a secure memory area in said terminal; calculating, by the terminal processor, a cryptographic digest Cnd_D i of each description of a right D i ; associating, by the terminal processor, an identifier Id_D i of the right D i with the identifier of the cryptographic digest Cnd_D i that generates a pair (Id_D i , Cnd D i ); associating, by the terminal processor, an identifier of at least one right D m with the identifier id RC k of said resource and/or content RC k in the secure memory area; transferring, by the terminal processor, the generated pair (Id_D i , Cnd D i ) into said secure memory area; transferring, by the terminal processor, a digest Cndc D m into in the secure memory area; verifying, by the terminal processor, that the identifier of at least one right D m is associated with the identifier Id RC k of said resource and/or content RC k in the secure memory area; verifying, by the terminal processor, that the description of the right D m corresponds to a requested use of the resource and/or content RC k ; recalculating, using the security module a cryptographic digest Cndc_D m of the right D m stored in the terminal; comparing, by the terminal processor, the recalculated digest Cndc_D m with the digest Cndc_D m 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_D m is identical to the digest Cnd_D m memorized in the secure memory area.