A method for secure processing of access controlled audio/video data (DATe) by a processing unit comprising a first conditional access device connected to a second conditional access device provided with a descrambler (DESC) and a secured processor or secure hardware logic, said processing unit receiving encrypted control messages the method comprising: - receiving a control message by the first conditional access device, said control message being structured as a conventional control message with a first part including first access conditions and, in place of the control word of the conventional control message, a second part structured as a control message including a control word, - decrypting the control message with a key specific to the first conditional access device and verifying authenticity of said control message with first authentication data associated to the control message, - verifying the first access conditions of the control message in relation to content of a memory of the first conditional access device and when the verification is successful, transmitting the second part to the second conditional access device, the method is characterized in that it comprises steps of: computing, by the first conditional access device, the second access conditions by applying a function to the first access conditions, obtaining resulting second access conditions AC2=F, and transmitting, by the first conditional access device, the second part including the resulting second access conditions AC2=F to the second conditional access device. - receiving the second part by the second conditional access device, - decrypting the second part with a key specific to the second conditional access device and verifying authenticity of said second part with second authentication data associated to the second part, - verifying the second access conditions of the second part in relation to the contents of a memory of the second conditional access device and when the verification is successful, releasing and loading the control word into the descrambler (DESC), - descrambling the access controlled audio/video data (DATe) by using the control word and providing said audio/video data in clear (DATc) to an appropriate output of the processing unit. - receiving a control message by the first conditional access device, said control message being structured as a conventional control message with a first part including first access conditions and, in place of the control word of the conventional control message, a second part structured as a control message including a control word, - decrypting the control message with a key specific to the first conditional access device and verifying authenticity of said control message with first authentication data associated to the control message, - verifying the first access conditions of the control message in relation to content of a memory of the first conditional access device and when the verification is successful, transmitting the second part to the second conditional access device, computing, by the first conditional access device, the second access conditions by applying a function to the first access conditions, obtaining resulting second access conditions AC2=F, and transmitting, by the first conditional access device, the second part including the resulting second access conditions AC2=F to the second conditional access device. - receiving the second part by the second conditional access device, - decrypting the second part with a key specific to the second conditional access device and verifying authenticity of said second part with second authentication data associated to the second part, - verifying the second access conditions of the second part in relation to the contents of a memory of the second conditional access device and when the verification is successful, releasing and loading the control word into the descrambler (DESC), - descrambling the access controlled audio/video data (DATe) by using the control word and providing said audio/video data in clear (DATc) to an appropriate output of the processing unit. - receiving the second part by the second conditional access device, - decrypting the second part with a key specific to the second conditional access device and verifying authenticity of said second part with second authentication data associated to the second part, - verifying the second access conditions of the second part in relation to the contents of a memory of the second conditional access device and when the verification is successful, releasing and loading the control word into the descrambler (DESC), - descrambling the access controlled audio/video data (DATe) by using the control word and providing said audio/video data in clear (DATc) to an appropriate output of the processing unit.