As our aging population significantly grows, personal health monitoring is becoming an emerging service and can be accomplished by large-scale, low-power sensor networks, such as Zigbee networks. However, collected medical data may reveal patient privacy, and should be well protected. We propose a Hierarchical and Dynamic Elliptic Curve Cryptosystem based self-certified public key scheme (HiDE) for medical data protection. To serve a large amount of sensors, HiDE provides a hierarchical cluster-based framework consisting of a Backbone Cluster and several Area Clusters. In an Area Cluster, a Secure Access Point (SAP) collects medical data from Secure Sensors (SSs) in the sensor network, and transmits the aggregated data to a Root SAP located in the Backbone Cluster. Therefore, the Root SAP can serve a considerable number of SSs without establishing separate secure sessions with each SS individually.
To provide dynamic secure sessions for mobile SSs connecting SAP, HiDE introduces the Elliptic Curve Cryptosystem based Self-certified Public key scheme (ESP) for establishing secure sessions between each pair of Cluster Head (CH) and Cluster Member (CM). In ESP, the CH can issue a public key to a CM, and computes a Shared Session Key (SSK) with that CM without knowing the CM’s secrete key. This concept satisfies the Zero Knowledge Proof so CHs can dynamically build secure sessions with CMs without managing a CM’s secrete keys. Our experiments in realistic implementations and Network Simulation demonstrate that ESP requires less computation and network overhead than the Rivest-Shamir-Adleman (RSA)-based public key scheme. In addition,security analysis shows keys in ESP are well protected. Thus, HiDE can protect the confidentiality of sensitive medical data with low computation overhead, and keep appropriate network performance for wireless sensor networks.