Patent ID: 7742600

Claim:
A system comprising: a managing center, the managing center being configured to transmit, via a broadcasting channel, a data stream encrypted by control words, the control words being included in control messages; at least one user unit configured to receive said data stream; and a security module linked to the at least one user unit; the security module being configured with a unique address, the security module containing a credit, the security module being configured to decrease the credit according to the purchase of products or to the consumption of the data stream in an amount relating to a product or a duration, said amount and/or duration being defined in the control message or in a management message, the security unit further being configured to increase the credit in response to an encrypted message received from the managing center via the broadcasting channel, the credit being increased in an amount indicated by the encrypted message; wherein the managing center is configured to receive, from a user using a communication channel separate from the user unit and distinct from the broadcasting channel, an identifier representative of the unique address and a value code representing an amount of a credit to reload, the value code being unique and providing access rights to the product, a set of products or the duration, the managing center being configured to accept the value code only once and to process and verify the value code and to transmit to the security module, via the broadcasting channel, an encrypted message comprising the unique address and indicating the amount of the credit to reload into said security module.