# Key Management Scheme Based on Route Planning of Mobile Sink in Wireless Sensor Networks
## 2 Related Work  
MSs can prolong the survival time of WSNs and balance the nodes' energy consumption. For MS route planning, some research conclusions had been reached by other scholars. [PERSON] _et al._[5] proposed a network model in which nodes deliver data to the nearest fixed sink node with multiple hops, and then the MS collects data by traversing all the fixed sink nodes. This scheme turns the problem of MS route planning into a Traveling Salesman Problem (TSP) with the limitations of the MS's moving speed and node's memory space. However, this method needs to visit all the sink nodes, so it will increase the MS movement path, and fails to make full use of the communication capacities among the nodes. By gridding the network, [PERSON] _et al._[6] divided the network into several virtual network points, and elect the cluster head based on the weighted sum of the residual energy and the distance from the nodes to the center of gravity of the cluster. This can avoid the nodes with lower energies from becoming the cluster head. Finally the sink nodes can be scheduled to receive the collected data from the cluster heads by the controllable moving strategy, and this can save the energy consumption of the network. [PERSON] _et al._[7] used the grid clustering method, in which the main cluster head and the deputy cluster head are introduced to communicate and collect data, and the sink node collects data along with the scheduled centers of the grids. [PERSON] _et al._[8] limited the distance between each node and the cluster center within the maximum communication distance, and then the detection area will be clustered. The MS visits the cluster center for data collection according to the optimal moving path using a TSP method. [PERSON] _et al._[9] considered the influences of energy consumption and data delay on the process of route choice, and a mathematical model was built for the relationship of energy consumption and data delay based on boundary hop counts. [PERSON] _et al._[10] proposed the disk clustering method. The data collection points were selected according to nodes' specific locations, and the MS will visit the collection points by the optimal route which is solved by a quantum genetic algorithm. All the above research only considers the routing protocol and data collection based on the optimal MS path planning, rather than comprehensively considering the network energy consumption, the survival time and any safety issues, _etc._  
The core of the security problem of WSNs is how to safely establish the session keys, which is the vital process to ensure the safety of data collection and transmission. For the sensor nodes whose resources are constrained, the complex encryption algorithms used in traditional networks cannot be directly transplanted to a WSN. Therefore, under the premise of network security, lightweight schemes should be considered preferentially. Symmetric key systems and asymmetric key systems are widely used in technology encryption systems. Random key pre-distribution and pre-allocated polynomial keys are typical methods used in symmetric key systems. In the Eschenauer and Gligor(EG) scheme [11], partial keys are randomly selected from a key pool generated by the server to build the key ring. The nodes can set up a secure communication link when the adjacent node finds that the same key exists in the key ring. [PERSON] _et al._[12] proposed an improved random key distribution scheme called \(q\)-composite key pre-stored scheme. This scheme requires that security key links can be set up only when adjacent nodes share at least \(q\) identical keys. Obviously, this scheme improves the resilience ability of the network, but the redundancy of keys increases, and it is not conductive to the expansion of the network. [PERSON] _et al._[13] proposed the Authentication and Pairwise (AP) key scheme.