A content transmitter apparatus to deliver content to a content receiver apparatus through a network, comprising: a device authentication processing portion to authenticate the content receiver apparatus and create key information to be shared with the content receiver apparatus; an encryption processing portion to encrypt the content to be delivered to the content receiver apparatus by using the key information; a communication processing portion to transmit and receive authentication data to and from the content receiver apparatus and transmit the content to the content receiver apparatus via the network; and a controller to control the device authentication processing portion, the encryption processing portion and the communication processing portion; wherein the controller registers device information of the content receiver apparatus; wherein, when the content encrypted by the encryption processing portion is delivered through the communication processing portion to the content receiver apparatus located outside a house, the controller authenticates the content receiver apparatus according to a first authentication method and transmits the key information, the first authentication method including a procedure that authenticates the device if it is decided, based on the registration information, that the content receiver apparatus is a registered device; wherein, when the content encrypted by the encryption processing portion is delivered through the communication processing portion to the content receiver apparatus located inside the house, the controller authenticates the content receiver apparatus according to a second authentication method and transmits the key information. a device authentication processing portion to authenticate the content receiver apparatus and create key information to be shared with the content receiver apparatus; an encryption processing portion to encrypt the content to be delivered to the content receiver apparatus by using the key information; a communication processing portion to transmit and receive authentication data to and from the content receiver apparatus and transmit the content to the content receiver apparatus via the network; and a controller to control the device authentication processing portion, the encryption processing portion and the communication processing portion; wherein the controller registers device information of the content receiver apparatus; wherein, when the content encrypted by the encryption processing portion is delivered through the communication processing portion to the content receiver apparatus located outside a house, the controller authenticates the content receiver apparatus according to a first authentication method and transmits the key information, the first authentication method including a procedure that authenticates the device if it is decided, based on the registration information, that the content receiver apparatus is a registered device; wherein, when the content encrypted by the encryption processing portion is delivered through the communication processing portion to the content receiver apparatus located inside the house, the controller authenticates the content receiver apparatus according to a second authentication method and transmits the key information.