Many emerging application domains are being developed for smart living environments. In particular, smart living environments that provide assistance for aging populations are becoming increasingly feasible. Therefore, there is an urgent requirement for a ubiquitous health monitoring (UHM) system. The proposed authentication scheme for UHM system consists of a wireless body area network, inexpensive sensors, a personal mobile device, and a medical server. To prevent fraudulent behavior, the mutual authentication between elements is necessary. However, the current security mechanism for UHM system is not clearly described. In such a way, a secure authentication for UHM system is proposed which can protect the patient-data well and is suitable for currently available wireless sensors.