Research On Some Key Security Issues For Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are made up of a great number of cheap micro-sensors in a monitoring area. They work as multi-hop and ad hoc networks using wireless channels to communicate with each other. WSNs are used to sense, collect and process data in the coverage area and then send the collected data to the observers. In return, the users send back commands to the sensors or actuators to control different operations. Besides its wide military application, the use of wireless sensor networks has also grown rapidly in the civil fields such as monitoring environment and ecology, healthcare, modern agriculture, home automation and intelligent traffic control etc. A remarkable attention has been paid to the features of WSNs such as low-cost, low-power, small in size, quick to deployment and robustness. America Business Weekly Magazine pointed out that wireless sensor network is one of the 21 most effective and powerful technology in the 21st century. And MIT's Technology Review Magazine also declared that wireless sensor network is one of the 10 emerging technology that will change the word.At present, security issues for WSNs are the most important factors considered in the military application field, which are yet often ignored for the reasons of economic accounting or the limitation on low-cost nodes in most civil fields. However, in some civil fields such as healthcare or home security application areas, people now pay more and more attentions on security issues because of individual privacy and sensitive data. we can conclude that security issues are and will continue to be the bottleneck of wide applications of WSNs, and the poor security scheme will limit their broad applications.Therefore, some key security issues for WSNs are discussed in this dissertation: two new data encryption algorithms, a hybrid key management scheme and a lightweight intrusion detection system in the condition of limited resources of WSNs. We have used all these three security issues for a project named "A digital community healthcare monitoring system based on WSNs" and have made the system more reliable, secure and available.Firstly, the importance of security for wireless sensor networks is discussed from the view of application requirement and confidentiality is considered to be the most basic and important feature in a wireless communication system. After analyzing the advantages and disadvantages of symmetric cryptography and asymmetric cryptography, two novel algorithms named as SF_noSBox and SF_SBox are proposed under the limitation on power, storage and processing capabilities of nodes in WSNs. These two algorithms are compared and analyzed with DES from the view of algorithm complexity and storage requirements. The experiment results show that the new two algorithms are feasible and have some better performance than DES in running times and storage requirements.Secondly, according to the requirements of security issues for WSNs, a new key management scheme based on Elliptic Curve Cryptography (ECC) is proposed. The new scheme is named as HKM_ECC (Hybrid Key Management based on ECC) for good performance and security in WSNs. Its main design principle is to exchange and authenticate keys using ECC scheme efficiently and to encrypt sensitive data using symmetric cryptography algorithm fast. These keys used for symmetric cryptography algorithms are encrypted, broadcasted and managed by ECC scheme. The encryption procedure takes only once to exchange this short key (128 bits). It will not decrease the performance of system even using the complex algorithms like ECC. This hybrid scheme takes more advantage above the pure symmetric cryptography or pure asymmetric cryptography schemes in algorithm performance and storage requirements. The experiment results show that this hybrid scheme is feasible.Thirdly, Intrusion Detection System (IDS) in WSNs is discussed with Game Theory approach. A new method using multi-nodes to determine one suspicious node within a cluster is proposed. After collecting all its neighbor's decisions, a node will be treated as a malicious one or normal one by the cluster-head using vote principle. And the vote result will be broadcasted to all nodes within this cluster. The detection rate and false positive rate of one node will affect the detection result mostly when this one node is used to determine the suspicious node. The detection precision will be increased fast when multiple neighbor nodes take part in this process. For example, when above 25 nodes treat the suspicious node as a malicious node in total 35 nodes with simple'majority vote, we can deduce that this node is mostly a malicious one. The experiment results also show that it is feasible and effective to use Game Theory approach in WSNs.Lastly, the two novel encryption algorithms and the hybrid key management scheme mentioned above have been applied in designing and implementing a real project named as "A digital community healthcare monitoring system based on WSNs". The system has been designed with some key security issues and received positive society fame.