In one aspect, a video processing device includes a processor and a transmitter, for example implemented as separate integrated circuits on a printed circuit board. Pins on the processor are coupled to pins on the transmitter via a data channel, for example conductive leads on the printed circuit board. Video data is transmitted from the processor to the transmitter via this data channel, which is high speed enough to accommodate video data. The transmitter also includes an encryption engine used to encrypt the video data. Encryption control data, which determines the encryption to be applied, is transmitted from the processor to the transmitter over the same data channel as the video data. This is more secure than transmitting the encryption control data over a slower separate data channel, because the high speed video channel is harder to tamper with.