In a display device that is daisy-chained to a source device that outputs a video signal, and transmits an encryption key (KSV) used for encryption to source device, the display device includes storage to store the encryption key of an own display device (first device KSV), and the encryption keys (second device KSV, third device KSV) of all of downstream side display devices that are provided on a downstream side of the own display device among all of the other display devices that are daisy-chained, the encryption keys being transmitted to source device through its own display device when the display devices are daisy-chained to source device, and causes a display to form a split video image that is a part of a video image based on the number of splits of the video image corresponding to the video signal and the number of encryption keys stored.