Research On Key Predistribution Schemes Based On Combinatorial Designs For Wireless Sensor Networks

With more and more extensive applications of wireless sensor networks(WSNs)in both civilian and military areas,more and more attention is paid to the security problems of them.Encryption technology provides the foundation for a number of security techniques and key management is a key problem of encryption technology.So key management plays an important role in the security of WSNs.Under normal circumstances,before the deployment of WSNs,the information on deployment is unpredictable.In order to solve this problem,key predistribution schemes(KPSs)are proposed.WSNs have some characteristics and limitations which make the metrics for evaluating KPS s are conflicting.Hence it has always been a concerned issue that how to design suitable KPSs for WSNs in different application scenarios.The main contributions of this dissertation are using combinatorial designs to construct secure and effective KPSs.The concrete content is summarized as follows:1.A KPS based on mixed-level orthogonal arrays(OAs)is proposed,where the mixed-level OAs are obtained from a class of saturated symmetric OAs by using Kronecker sum.In the scheme,any two nodes have common keys,i.e.,the direct connective probability is equal to 1.So the path-key establishment phase does not take place.For the same number of sensor nodes,there may be several choices for the parameters so that we can obtain different schemes and this makes the construction method more flexible.We analyze the resulting scheme and compare it with existing ones.The results show that for given numbers of nodes,the proposed scheme has either better connectivity and resilience or lower key storage.2.For a WSN which uses a trusted base station and an authenticated broadcast channel,a broadcast-enhanced KPS based on OAs is proposed.In this scheme,we still use logical key hierarchy(LKH)schemes for the underlying layer to revoke nodes more efficiently,but for the temporal layer,we use KPSs based on OAs.The connectivity,resilience and broadcast load of the resulting scheme are analyzed and comparison between it and the existing one is made.It is found that the proposed scheme has better connectivity and resilience than the existing one when the number of nodes per LKH tree is low.3.A KPS based on combinatorial designs for two-layer hierarchical WSNs is proposed.In a two-layer network,a small percentage of sensor nodes have more capabilities.In the scheme,first an OA is used to construct a KPS,then the sets of keys associated with a block and a random subset of a block are assigned to a more capable node and a less capable node,respectively.In some different network models,analysis of the resulting scheme is given and comparisons between the proposed scheme and random schemes are made.It is found that the resulting scheme has better resilience and for a given key storage,the proposed scheme can provide a better tradeoff between direct connectivity and resilience.4.Hash-chain improvement of KPSs based on transversal designs(TDs)is proposed.Two methods based on hash chains are applied on the KPSs based TDs.The improved schemes increase the resilience of the initial scheme at the cost of a few additional computations,while maintaining the connectivity at the same level.We analyze the improved schemes and compare them with existing ones.The results show that for given key storage,direc-t connective probability and the length of hash chains,the resulting schemes have better resilience.