METHOD AND PROCESSING UNIT FOR SECURE PROCESSING OF ACCESS CONTROLLED AUDIO/VIDEO DATA

摘要

A method for verifying access conditions performed by two conditional access devices consecutively on a control message before releasing a control word to a descrambler. The control message includes a first part including first access conditions and a second part structured as a control message including at least second access conditions and a control word. A first conditional access device is configured for decrypting the control message with a common key specific to units having a first conditional access device and verifying the authenticity of said message. When the verification succeeds, the second part and a second right is transmitted to a second conditional access device, which decrypts the second part with a common key specific to units having a second conditional access device and verifies the authenticity of said second part and the second access conditions in relation to the second right encrypted by a personal key embedded therein.