## 1 Introduction  
The ever-increasing advancement in information and communication technologies has led to a new era in the successful development of IoT (Internet of Things)-based services, which extends the concept of the Internet and delivers versatile types of pervasive computing applications not seen in the past. In particular, in the modern healthcare environment, IoT-oriented technologies have brought novel opportunities for hospital administrators and physicians to provide on-demand and real-time body-care services to those (usually the patient) in need of higher accuracy and better efficiency. The architecture of the body sensor networks (BSNs) is a collection of tiny and low-powered wireless body sensors for monitoring the patient's health status in a real-time manner. BSNs have become one of the most popular core technologies in developing IoT-based healthcare applications. For example, the patient's bio-features can be monitored in real time via bodily equipped or embedded bio-sensors. The physicians (or nurses) can thus assess the personal health status of their patients more effectively. Medical errors can be avoided, and the treatments provided by the hospital will be more on-demand in nature. Furthermore, with pre-defined system settings tailored to the patient, potential critical emergencies experienced by the patient can be prevented more effectively. Bio-sensors for detecting electrocardiography (ECG), electroencephalography (EEG), electromyography (EMG), blood pressure (BP), temperature and motion have been commercialized for end users in this IoT concept-oriented generation. It is highly exciting to see the opportunity for developing and deploying an IoT-based healthcare system providing significant benefits to patients in the real world. Healthcarehas thus advanced to a new era with a whole new perspective on the application development of IoT-based architectures. While IoT-oriented techniques have brought the opportunity for innovative application development, this opportunity has also brought new security challenges to IoT-based applications. For instance, _Hello Barbie_, a novel IoT-based commercial product for children, reveals a potential privacy threat, which allows the attacker to spy on us, our family and everything via camera and voice-interaction functionalities in the house [1]. In general, every sensor in the IoT represents a potential risk of system vulnerability. That is, each sensor may be a vulnerable entry point for malicious attacks. The security issue, i.e., how to effectively protect an IoT system with an appropriate security level, i.e., providing data confidentiality, integrity and privacy during data collection, has been promptly focused on during these years. The academic community has put great efforts into this important and promising research field. There seems to be a general expectation for a new and revolutionary security solution tailored to IoT-based sensors. However, because the sensors adopted in IoT applications usually have a specific defined mission with limited resources available to accomplish it, the traditional security solutions, such as firewalls, Intrusion Detection System (IDS) and Intrusion Prevention System (IPS), are not suitable for implementation on these kinds of sensors. Hence, the refinement of traditional security solutions to fit specific security requirements of IoT-based sensors is one of the most promising ways for securing IoT-based application systems. Based on our observations, great efforts have been put into the development of secure IoT-based systems. In 2013, [PERSON] et al. [2] proposed a lightweight authentication scheme for secure multicast functionality in small-scale IoT networks. The proposed mechanism mainly utilizes two effective properties, i.e., (1) the absorbency property and (2) the one-way or quasi-communicative property, of a fast accumulator refined by them to establish a lightweight multicast authentication scheme.