| 摘要 |
A method and a device for permission conditional access are provided to prevent an encrypted digital data product from being not accessed for a long time due to expired qualifications, which are not periodically updated. A permission device(19) includes a secure memory(21) storing at least one qualification set and an interface(22) including the device(25) decrypting the encrypted digital data products. Each qualification includes a product data and the expiration information. The interface enables the permission device to receive qualification control messages including the product ID. In a first mode, the permission device returns at least one control word if the product ID corresponds to the product ID of the stored qualification, which includes the expiration information for validating the product ID, in response to the qualification control message received through the interface. In a second mode, the permission device sequentially adjusts a counter with a predetermined value and returns at least one word if the product ID included in the received qualification control message corresponds to the product ID of the stored qualification. |
