# Information-Aware Secure Routing in Wireless Sensor Networks
## 1 Introduction  
Wireless sensor networks (WSNs) have emerged as a promising technology for various application scenarios, such as battlefield monitoring, emergency response, environmental monitoring, and healthcare monitoring. However, WSNs are vulnerable to various threats because they are usually deployed in a hostile or harsh environment [1]. Sensor nodes in WSNs are captured relatively easily by attackers, and then act as malicious nodes that launch various attacks, such as selective forwarding, wormhole, sinkhole, hello flooding, and Sybil [2; 3; 4]. Malicious nodes drop some or all packets, so some important data cannot reach the sink node if the routing protocol is not immune to such attacks. Even worse, the network might partly or completely fail. The traditional routing mechanisms were designed for data transmission and are thus not applicable to WSNs in the presence of malicious nodes. Furthermore, routing in WSNs is constrained by the energy and computing capacities of sensor nodes. In recent years, the routing security of WSNs has become a hot research topic [5; 6; 7]. The existing routing protocols for WSNs cannot effectively balance security and energy consumption [8; 9; 10]. Most of these protocols rely on encryption and trust mechanisms to guarantee security. Although encryption can help WSNs to resist specific types of network attacks, the routingprotocols embedded with encryption are vulnerable to other types of network intrusions, which will result in more energy consumption. With more routing paths, we can improve the resilience of these protocols, but the construction and maintenance of extra routes result in more consumption of the energy and storage space of sensor nodes. Trust-based routing protocols can resist various types of attacks, but the calculation of trust values always uses very high memory and consumes substantial energy. The existing routing protocols are typically optimized for energy consumption; thus, a complete route for a pair of nodes is normally generated by augmenting the current path one hop at a time. However, the generated routes are not globally optimal and may fail to work in the presence of malicious attacks. Therefore, it is very hard for existing routing protocols to find a secure route that can balance security and the constraints on the computing and battery capacities of WSNs. In this paper, we propose a new secure routing protocol for WSNs in the presence of malicious nodes. The protocol finds a secure route by taking into account both the trust value and the status of each relay node in the route. We use attack probability to represent the trust of each sensor node, and the trust value is calculated by the historical communication behaviors of the sensor node and the trust information of its neighbors. With the trust value, we can forecast the future behaviors of the sensor node. Furthermore, we can use the associated information of the sensor nodes to establish a secure route for data transmission between a pair of sensor nodes, which can effectively eliminate interference from malicious nodes. Some sensor nodes may have incomplete information, so we also leverage the indirect trust value from other nodes to enhance the accuracy of the direct trust value. Our secure routing protocol chooses one sensor node at a time to improve the success rate of data communication without identifying the type of attack. In particular, a sensor node that has more residual energy and is closer to the sink node is selected as the next relay node. Thus, we can reach a trade-off between security and energy consumption for each sensor node. In addition, all secure routes are constructed via the serial-parallel system theory of the classical reliability theory, which guarantees the global optimization of our solution. It is able to not only resist various attacks, but also to choose a route with little interference and no fault in the wireless communication environment.