## 7 Related Works  
This section discusses the recently published literature on secure healthcare monitoring using wireless sensor networks. In [9] [PERSON] _et al._ proposed a biometric based distributed key management protocol, named BARI+, for wireless body area networks. The BARI+ architecture consists of a PS (personal server), MS (medical server), and WBAN (wireless body area network). In their scheme the WBAN is managed by four keys, namely, communication key, administrative key,basic key, and secret key that shared by sensor node and medical database/server. The BARI+ protocol is divided into three phases: (i) _initial deployment phase_: all initial keys are deployed in the PS, MS and WBAN in this phase; (ii) _re-keying phase_: in order to refresh the communication key, PS computes a value from the patient's biometrics, encrypts it, and broadcasts it into the network; and (iii) _node addition phase_: if a new node is added then the MS informs the PS about new deployments by sending identities, basic keys and other relevant information of the new node to the PS. Further, the authors claim that their protocol facilitates many security services such as confidentiality, authentication, and security against replay attacks, forward secrecy, security against node compromise and security against routing attacks. [PERSON] _et al._ simulated their scheme for Mica2 more and they used RC5 block cipher for confidentiality and SHA-1 for hashing. [PERSON] _et al._[32] proposed a lightweight middleware for personal wireless body area networks. The idea of the proposed middleware is to simplify and accelerate the development of wireless healthcare applications by using highly reusable codes. The middleware architecture has the following features: data acquisition, on-the-fly sensor reconfiguration, plug-and-play capabilities and resource management. In addition, it also provides security to protect critical sensor data from unauthorized parties. The authors choose SkipJack 64-bit lightweight block cipher cryptosystem for confidentiality, which consumes 622 bytes of ROM. For the performance evaluation three BSN accelerometers and one ECG were used as a prototype. The proposed middleware resides in a personal digital assistant (PDA). [PERSON] _et al._[56] proposed secure access to a hierarchical sensor-based healthcare monitoring architecture. The healthcare architecture is composed of three network tiers (sensor, mobile, and back-end network) and has been demonstrated for three different pervasive healthcare applications (in-hospital, in-home, and nursing-home). In the _sensor network tier_, a wearable sensor system (WSS) using Bluetooth and integrated with biomedical sensors is used to monitor the vital signals of individuals. Wireless sensor motes [WSMs (_i.e._, Mica2)] are placed within the building to collect the environmental parameters. WSS and WSM securely broadcast physiological information and environmental parameters to the upper layer. WSS uses an advance encryption standard (AES) based authentication (_i.e._, CBC-MAC) and an encryption scheme, while the WSMs use a polynomial-based encryption scheme to establish secure point-to-point communication between two WSM motes. A public-key based key establishment protocol is used to establish the secure keys. In _the mobile computing network tier_, mobile computing devices (MCD) such as PDAs organized as in an _ad-hoc_ network, route the data via multi-hops to the local station. MCD has the computational capabilities required to analyze the WSS and WSM data. A mobile-to-mobile text-based alarm message is used to show any real time abnormalities. Every MCD supports secure short message service (SMS) using cellular networks. Further, the authors used the ARAN routing protocol which is based on an _Ad Hoc_ On-Demand Distance Vector (AODV) routing protocol for _ad-hoc_ networks. The back-end tier is structured with a fixed station and server that provide application level services for lower tiers and process various sensing data.