A method of temporarily registering a second device with a first device, wherein the first device includes a temporary registration mode, the method comprising: activating the temporary registration mode in the first device; initiating a temporary registration operation in the first device from the second device, wherein in the second device, generating a random number for the second device and a random number for each input apparatus in an input apparatus list of the second device; encrypting the generated random number for the second device and the input apparatus list including the random number for each input apparatus; and sending a message containing the encrypted random number for the second device and the input apparatus list including the random number for each input apparatus to the first device, wherein a registration personal identification number, registration PIN, is generated based on the message at the first device and displayed by the first device for entry into the second device; determining, by the first device, whether the second device is authorized to register with the first device based on a PIN entered at the second device corresponding to the registration PIN; temporarily registering the second device with the first device in response to a determination that the second device is authorized to register with the first device; following at least one of a termination of a network connection between the first device and the second device and a powering off of at least one of the first device and the second device: terminating the temporary registration; and deleting, by at least one of the second device and the first device, information required for the temporary registration. activating the temporary registration mode in the first device; initiating a temporary registration operation in the first device from the second device, wherein in the second device, generating a random number for the second device and a random number for each input apparatus in an input apparatus list of the second device; encrypting the generated random number for the second device and the input apparatus list including the random number for each input apparatus; and sending a message containing the encrypted random number for the second device and the input apparatus list including the random number for each input apparatus to the first device, wherein a registration personal identification number, registration PIN, is generated based on the message at the first device and displayed by the first device for entry into the second device; generating a random number for the second device and a random number for each input apparatus in an input apparatus list of the second device; encrypting the generated random number for the second device and the input apparatus list including the random number for each input apparatus; and sending a message containing the encrypted random number for the second device and the input apparatus list including the random number for each input apparatus to the first device, wherein a registration personal identification number, registration PIN, is generated based on the message at the first device and displayed by the first device for entry into the second device; determining, by the first device, whether the second device is authorized to register with the first device based on a PIN entered at the second device corresponding to the registration PIN; temporarily registering the second device with the first device in response to a determination that the second device is authorized to register with the first device; following at least one of a termination of a network connection between the first device and the second device and a powering off of at least one of the first device and the second device: terminating the temporary registration; and deleting, by at least one of the second device and the first device, information required for the temporary registration. terminating the temporary registration; and deleting, by at least one of the second device and the first device, information required for the temporary registration.