A video source device includes a cipher unit. The video source device uses the cipher unit to generate cipher bits for ciphering video to be transmitted to protect the video from unauthorized copying. The video source device authenticates video receiving devices using a symmetric ciphering/deciphering process that requires the video source device to generate and provide the video receiving device with a pseudo random number as the seed/basis number for the symmetric ciphering/deciphering process. The video source device is further provided with a state machine that controls the cipher unit to generate the required pseudo random number for the video source devices, thereby eliminating the need of having to provide separate circuitry to generate the required pseudo random numbers.