Exploiting unidirectional links for key establishment protocols in heterogeneous sensor networks

Wireless sensor networks are designed for outdoor environment surveillance and require benign coverage, steady working status and long lifetime, so they require efficient security services eagerly. Most security schemes work efficiently only when bidirectional links exist. So does key establishment protocols in WSNs. However, unidirectional links may emerge frequently. In traditional key establishment schemes, designers delete all the unidirectional links from the network. Hence, the sensors covered only by unidirectional links are excluded from the collaborating network, even if they are stable and energetic. The schemes shorten the lifetime and shrink the connectivity of the whole network. To improve the network connectivity and increase the number of useable sensors in the network, we design a key establishment protocol for heterogeneous sensor networks exploiting unidirectional links. We propose inter-cluster and intra-cluster key establishment schemes for clusters and their members, respectively. Intra-cluster scheme adopts key pre-distribution mechanism, where cluster members and the cluster heads choose different number of keys. The results show that it greatly increases the resiliency against node compromise. Inter-cluster scheme adopts ID-based cryptographic algorithm using pairing and obtain identity authentication and perfect resilience against node compromise. Finally, the simulation reveals our scheme can greatly increase the proportion of available sensor nodes and network connectivity, which will efficiently prolong the network lifetime.