Abstract: Example embodiments are directed to a digital audio/video (AV) data processing unit and a method of controlling access to the digital AV data. The processing unit of AV digital data includes a deciphering unit of the AV data, a decompression unit, an input/output interface of the processed AV data and communication device towards a security module. The deciphering and decompression units respectively include an encryption unit and a decryption unit, each having at least one personal key and a common encryption key. Deciphering the AV data using the control words and re-encrypting the deciphered AV data occurs only after a successful verification of the control word and the common key. After temporary storage, the re-encrypted AV data cannot be decrypted by the decryption unit unless the common key has been positively verified by the security module by way of a random number generated by the decryption unit.

Abstract: A digital audio/video data processing unit and an access control method to this data are disclosed. The processing unit of audio/video digital data encrypted with control-words coming from control messages includes a deciphering unit of the audio/video data, a decompression unit, an input/output interface of the processed audio/video data and communication device towards a security module. The deciphering and decompression units include respectively an encryption unit and a decryption unit each having at least one personal key and a common encryption key. It includes a secured transmission device of the common key and of the control word extracted from a control message between the security module, the deciphering unit and the encryption unit using the personal key of the encryption unit.