METHOD TO ENFORCE BY A MANAGEMENT CENTER THE ACCESS RULES FOR A BROADCAST PRODUCT

摘要

The purpose of this invention is to propose a manner to rely to a lesser extent on the security means of the receivers security module to enforce the access conditions defined in the key messages on one hand and to handle complex access conditions based on the characteristic and properties of the receiving device or the user of such a device on the other hand. It is therefore proposed a method to enforce by a management center the access rules for a broadcast product received by receivers, the access to said product being released by an access key, said management center managing a plurality of Boolean positive and negative attributes on receivers, the method comprising the steps of associating one positive Boolean attribute to one receiver entitled to said attribute and loading state to it; associating one negative Boolean attribute to said receiver not entitled to said attribute and loading state to it; defining at least a second broadcast encryption scheme targeting the set of the negative Boolean attributes and associating to each negative Boolean attribute the corresponding decryption key material; expressing the access conditions on a product as a Boolean expression on attributes by combining at least one of the positive Boolean attributes and at least one of the negative Boolean attributes by means of at least one of Boolean conjunction or disjunction; generating at least one cryptogram to be broadcasted to the receiver by encrypting the access key by means of the two combined broadcast encryption schemes according to the said Boolean expression.