Systems and methods that protect transport stream content are disclosed. The system may include a first module and a second module, the first module having a common interface. The second module is coupled to the first module via the common interface. In one embodiment, the first module is a set top box, and the second module is a conditional access card. In one example, the first module demodulates an incoming transport stream, copy protection encrypts the demodulated transport stream and passes the copy protection encrypted transport stream to the second module via the common interface. The second module copy protection decrypts the transport stream received from the first module, conditional access decrypts at least some of packets of the transport stream that were conditional access encrypted, copy protection encrypts the transport stream and passes the copy protection encrypted transport stream to the first module via the common interface.