Combinatorial designs are powerful mathematical tools with comprehensive and simple algebraic structures. Recently, many researchers have used combinatorial designs as key predistribution schemes in wireless sensor networks (WSNs). Previous studies on security of WSNs are mainly concentrated on those networks containing nodes with the same capabilities. Further, investigations reveal that high reliability and lifetime on networks can be achieved through hierarchical heterogeneous wireless sensor networks, where a small number of sensor nodes have more energy, memory, and transmission capability. Inspired by scheme due to Lee and Stinson, we propose a key predistribution scheme for a clustered heterogeneous WSN using transversal designs. This proposed scheme assigns key chains to sensor nodes before deployment and separates key pool of each cluster by adding a pseudo-random generated number after deployment. The performance evaluation and security analysis show that our proposed scheme can provide better security with significant reductions on communication overhead and storage space than other key management schemes without compromising connectivity.Wireless sensor network security M. Javanbakht et al.problem of key establishment in sensor networks where each sensor node is preloaded with a finite set of keys prior to deployment. A key predistribution scheme (KPS) is a means of specifying which nodes store which keys.Key predistribution schemes can be random, deterministic, and hybrid. In random schemes, keys are randomly drawn from a key pool and are stored in each sensor node. This approach does not make sure whether every two nodes can communicate directly. If direct communication is not possible then a path needs to be established between two nodes. This path establishment decreasing the speed of communications increases power consumption. In deterministic schemes, deterministic methods are used to design key pool and key chains aiming at providing better key connectivity. In hybrid schemes, both deterministic and random approaches are combined to improve scalability and resiliency.Eschenauer and Gligor proposed a random KPS for distributed WSNs in [4]. In this scheme, at first, a large key pool is generated, and each sensor node is loaded with the fixed number of keys chosen randomly from this key pool along with their key identifiers. Then in key discovery phase, to find a common key, two nodes in their wireless communication range exchange the list of key identifiers from their own key chains. In case of sharing a common key, they can establish a direct secure communication. Otherwise, two nodes try to communicate with each other through a multi hop path. The proposed scheme in [4] provides good connectivity and resiliency but in shared key discovery phase, because two nodes have to exchange the list of their key identifiers to find the common key, the number of broadcast messages increases. This, in turn, enhances the communication complexity of protocol and decreases the battery's life.Combinatorial desi...