IMS USER EQUIPMENT, CONTROL METHOD THEREOF, HOST DEVICE, AND CONTROL METHOD THEREOF

An IMS User Equipment (UE) is provided. The IMS UE comprises: searching means for searching, based on UPnP technology, a UPnP network for a host device that has IMS subscription information, establishing means for establishing a session with the host device discovered by the searching means, subscription retrieving means for retrieving, from the host device via the session, the IMS subscription information, registering means for registering with the IMS network using the IMS subscription information, key retrieving means for retrieving, from the host device via the session, a first encryption key shared with an IMS application server (AS) in an IMS network by sending identity of the IMS AS to the host device via the session, and communicating means for performing encrypted communication with the IMS AS using the first encryption key.