| 摘要 |
<p>The invention aims at providing a novel manner of offering to a wide range of customers access to pay television while reducing costs related to subscriber management. This is achieved through a system comprising a management center (CAS) transmitting a data flow encrypted with control words (CW), said control words being included in control messages (ECM), said data flow being designed to be received by at least one user unit (STB) connected to a security unit (SC) identified by a unique address (UA), said security unit (SC) containing a credit (CR) which is decremented depending on the purchase of products or the consumption of the data flow. The invention is characterized in that the security unit comprises means for decrementing the credit by an amount (M1) corresponding to a product or by an amount (M2) corresponding to a time interval (T), said amount (M1, M2) and/or said time interval (T) being defined in the management message (ECM) or in a management message (EMM), the user being provided with means for communicating to the management center (CAS) an identifier representing the unique number (UA) and value code representing an amount (TA) for replenishing the credit (UA), the management center comprising means for processing and verifying the value code (VC) and for transmitting to the security unit (SC) an encrypted message comprising the unique address (UA) and the amount (TA) for replenishing the credit (CR).</p> |
