An input apparatus for selecting a content in a first user terminal device, selecting, from a first user interface, a first menu, wherein the first menu is for performing a function of transmitting the selected content, and selecting, from a second user interface, a second menu, wherein the second menu is for performing a function of receiving the selected content; the input apparatus being capable of receiving an input and comprising: a communicator configured to communicate with the first user terminal device and the second user terminal device; and a processor configured to: transmit, to the first user terminal device, a first control signal for displaying the first user interface on a screen of the first user terminal device; receive, from the first user terminal device, identifier information of the first user terminal device and an encryption key; transmit, to the second user terminal device, a second control signal for displaying the second user interface on a screen of the second user terminal device; and transmit, to the second user terminal device, the identifier information of the first user terminal device and the encryption key to initiate a pairing between the first user terminal device and the second user terminal device. selecting a content in a first user terminal device, selecting, from a first user interface, a first menu, wherein the first menu is for performing a function of transmitting the selected content, and selecting, from a second user interface, a second menu, wherein the second menu is for performing a function of receiving the selected content; the input apparatus being capable of receiving an input and comprising: a communicator configured to communicate with the first user terminal device and the second user terminal device; and a processor configured to: transmit, to the first user terminal device, a first control signal for displaying the first user interface on a screen of the first user terminal device; receive, from the first user terminal device, identifier information of the first user terminal device and an encryption key; transmit, to the second user terminal device, a second control signal for displaying the second user interface on a screen of the second user terminal device; and transmit, to the second user terminal device, the identifier information of the first user terminal device and the encryption key to initiate a pairing between the first user terminal device and the second user terminal device. a communicator configured to communicate with the first user terminal device and the second user terminal device; and a processor configured to: transmit, to the first user terminal device, a first control signal for displaying the first user interface on a screen of the first user terminal device; receive, from the first user terminal device, identifier information of the first user terminal device and an encryption key; transmit, to the second user terminal device, a second control signal for displaying the second user interface on a screen of the second user terminal device; and transmit, to the second user terminal device, the identifier information of the first user terminal device and the encryption key to initiate a pairing between the first user terminal device and the second user terminal device. transmit, to the first user terminal device, a first control signal for displaying the first user interface on a screen of the first user terminal device; receive, from the first user terminal device, identifier information of the first user terminal device and an encryption key; transmit, to the second user terminal device, a second control signal for displaying the second user interface on a screen of the second user terminal device; and transmit, to the second user terminal device, the identifier information of the first user terminal device and the encryption key to initiate a pairing between the first user terminal device and the second user terminal device.