Research On Key Management For Distributed Wireless Sensor Networks

Recent advances in wireless communications, computing technology, and micro-electro-mechanical systems technology have enabled the development of distributed wireless sensor networks, which is much attractive in military defence, environmental surveillance, health applications, and other commercial applications. However, due to its characteristic and environment, distributed wireless sensor networks are easily attacked, and sensor nodes could be physically compromised by an adversary. So Security in distributed wireless sensor networks is a key problem in the design of system.In the security framework of distributed wireless sensor networks, key management plays a fundamental role. Due to the intrinsic properties of distributed wireless sensor networks, such as large scale, the restriction of sensor nodes'resource, distributed deployment, etc., the traditional key management in wireless networks can not be suitable for it mechanically. Recently, researchers have proposed two kinds of key management schemes in distributed wireless sensor networks: random and deterministic algorithms. Though these protocols have been made progress in performance, they are difficult in trading off among network connectivity, resilience, and memory cost.Based on systematically studying and summarizing the relevant works on key management in distributed wireless sensor networks, this dissertation makes comprehensive studies on key predistribution and establishment based on random and deterministic algorithms in distributed wireless sensor networks, from the points of improving network connectivity, enhancing network resilience against node capture and reducing memory cost.The major contributions of this dissertation are as below:1. Study on random key predistribution in distributed wireless sensor networks There is a contradiction between security and network connectivity in the proposed schemes based on deployment knowledge. Thus, we propose a Polynomial-Pool-based Key Management scheme, PPKM. First of all, using group-based deployment knowledge, the depolyment region and sensor nodes are divided into several groups, respectively. Second, the setup server generates a global polynomial pool which is decomposed into many local polynomial pools. Third, each node forms its polynomial ring by randomly choosing the polynomials from its local polynomial pool, in addition, the network connectivity between any two nodes is decided by the overlapping factors. Due to only polynomial information in nodes before deployment, the shared keys can be generated by calculating the shared polynomials between any two neighboring nodes. The results indicate that this scheme not only levels off network connectivity but also greatly improves resilience against node capture.2. Study on random key establishment in distributed wireless sensor networksIn order to study on the performan by changing the network shape, we study a Triangle-based key establishment scheme. Triangle-based scheme which builds up an equilateral triangle grid model based on deployment information about expected locations of sensor nodes. Furthermore, Each triangle grid introduces a polynomial, and there are thirteen polynomial shares among each cell and its neighboring cells. Simulation results indicate that the algorithm can achieve the higher probability of direct key establishment and that of indirect key establishment. More importantly, by decreasing nodes'deployment density, decreasing the size of deployment model and increasing the polynomial degree, the probability of disclosed communication would be greatly reduced. So network security tolerance has been accordingly enhanced.3. Study on deterministic key predistribution in distributed wireless sensor networksThe deterministic key predistribution schemes based on the key pool are poor in resilience. Therefore, Blom matrix with the t -secure property is introudced to predistribute the keys, and we give a Blom-based Hexagonal Key Management scheme, BHKM. This scheme proposes a novel hexagon grid model which is divided into many non-overlapping hexagon grids, and applies Blom's scheme in each pair of neighboring grids. The research results illustrate that there is a good tradeoff in this scheme among network connectivity, resilience against node capture and memory cost .4. Study on deterministic key establishment in distributed wireless sensor networksIn the existing deterministic key establishment schemes based on the polynomial pool, the distribution and establishment of the polynomial pool is difficult. This chapter discusses a LU matrix decomposition-based Key Management scheme, LUKM. This scheme makes use of LU symmetrical polynomial matrix to guarantee that there is at least one shared polynomial between any pair of nodes. Compared with those schemes based on LU matrix decomposition, LUKM substitutes the polynomial pool for the key pool to establish the shared keys, and enhances the reilience against node capture. The analysis shows that not only this scheme appears the excellent network connectivity, but also develops an efficient encoding mechanism to optimize the network-wide memory overhead. In addition, this protocol improves the efficiency of polynomial distribution in the irregular region.