National Tsing Hua University
In a Universal Mobile Telecommunications System (UMTS), a User Equipment (UE) can access IP multimedia services through IP Multimedia Subsystems (IMS). In addition to passing IMS authentication, called IMS AKA, this UE also needs to pass General Packet Radio Service (GPRS) authentication, called 3GPP AKA, since the data of the IMS service is transmitted through a GPRS network. In this paper, the authors design an efficient IMS authentication scheme based on a trust relation between UE and Serving GPRS Support Node (SGSN) established in GPRS authentication. Compared with the conventional IMS authentication, their scheme can save up to 40% transmission and is analyzed as a secure scheme. Moreover, their scheme does not require any modification in the UE's authentication procedures.