METHOD FOR SECURING DATA EXCHANGED BETWEEN A MULTIMEDIA PROCESSING DEVICE AND A SECURITY MODULE

摘要

The aim of the invention is to provide a method for forming a secured and authenticated channel between a multimedia processing device and a security module dividable among several entities in such a way that the data transmitted to one entity does not affect the other entities. The aim is attained by a method for securing data exchanged between a multimedia processing device (STB) and a security module (M) managed by a management center, wherein said multimedia processing device (STB) receives the encrypted multimedia data flow for decrypting said data flow and converting it in such a way that it is readable and provided with a personal key (RK). The inventive method consists in obtaining an identifier (CAS ID) assigned to an entity which represents a group of multimedia processing devices by said multimedia processing device (STB), in computing a security key (VK) formed by a one-way operation which is based on the personal key (RK) of the multimedia processing device (STB) and the entity identifier (CAS ID), in transmitting said security key (VK) to the security module (M) assigned to the entity, in forming the security key (VK) with the aid of the processing device (STB) by receiving the entity identifier (CAS ID) thereby, in computing said security key (VK) by the multimedia processing device (STB) using the one-way operation which is based on the personal key (RK) thereof and the entity identifier (CAS ID) and in using said security key (VK) for securing the data exchanged between a multimedia processing device (STB) and the security module (M).