Research On Key Technologies Of Key Management For Wireless Self-organizing Networks

Wireless self-organizing networks(WSONs)are formed by self-organization among wire-less nodes,which are distributed and highly dynamic.Mobile ad hoc networks(MANETs)and wireless sensor networks(WSNs)are two popular WSONs that have attracted many attentions.Due to flexible deployment,WSONs have been used in many fields.However,properties of WSONs and the inherent openness of wireless channels make WSONs vulnerable to many se-curity threats.Therefore,security of WSONs is an attractive issue.Since that current security mechanisms are based on cryptography,key management is critical for WSONs security.Taking the application environments into consideration(MANETs or WSNs),this dissertation focuses on key management and its key technologies in WSONs.The main contents are as follows:(1)According to the characteristics of WSNs,a dynamic key management scheme based on EBS is proposed,called t-EEBS.After analyzing properties of EBS and collusion attack,a target key ring collection construction process is implemented during key management.Then,the resistance of collusion attack can be greatly enhanced when an appropriate key ring in the generated collection is distributed to each node.Specifically,two algorithms,the heuristic algo-rithm and the statistical algorithm,are proposed to implement the aforementioned construction process.Moreover,the construction process of the special case is also analyzed,where no more than 2 nodes are colluding.The entire key management mechanism is implemented based on the construction process.Simulation results show that the resistance against collusion of the pro-posed scheme is better than other EBS-based schemes.The proposed scheme can provide better security service for WSNs.(2)Due to poor key connectivity,many excellent key management schemes are not avail-able although they have many favorable characteristics.To enhance key connectivity of such schemes,a key generation method based on system of equations is proposed.In this method,the key pool of the given network is formed by the system of equations that has a unique solution and each involved equation is used to establish a key in the key pool.The unique solution of the system of equations can be used as the hidden shared secret to strengthen the association among nodes.Such keys are called associated keys.The proposed method can be efficiently combined with key management mechanisms and enhance their key connectivity.Theoretical and simulation results show that,comparing with normal keys,key management schemes with associated-keys have better key connectivity and thus significantly enhance the efficiency of secure communication.(3)Although physical layer key generation ensures that nodes can directly establish shared secret keys from wireless channel,channel variations significantly affect the efficiency of key generation.If channel measurement sequences lack variations,the randomness of the shared key cannot be guaranteed.Moreover,the implementation of key generation might become more difficult as long as sequences of transceivers might have too many discrepancies.Accordingly,a physical layer key generation scheme based on the Rnyi entropy of order 2(collision entropy)is proposed.During key generation,the entire sequence is divided into several sub-sequences of same length.Then,entropy of each sub-sequence is calculated to determine its availability.Con-sequently,some sub-sequences with smaller entropies are discarded.To validate the proposed scheme,several experiments in different scenarios are conducted by laptops with different wire-less cards.The results of real environmental experiments show that the bit mismatch rate of the proposed scheme is lower than the classic adaptive scheme.The generated secret keys can be used to achieve secure communication between nodes.(4)According to existing schemes and experiments in real environments,channel mea-surement sequences of transceivers might have too many discrepancies due to the half-duplex communication and other interferences.After quantization,these discrepancies might produce many mismatches between bit sequences and further affect the efficiency of key generation.To reduce such discrepancies,a key generation scheme based on the discrete wavelet transform(DWT)is proposed.After collecting sufficient channel measurements,transceivers separately use the same DWT process to eliminate some small-scale fluctuations and the output of DWT is used as input of the following process.Comparing with original sequences,outputs of DWT processes performed by the involved transceivers have higher correlation.With the implementa-tion of uniform quantization,the shared key can be generated.The results of experiments show that the bit mismatch rate is significantly reduced by the pre-processing of DWT.The proposed scheme can efficiently generate shared secret keys for wireless nodes.