# An Efficient Trust-Based Scheme for Secure and Quality of Service Routing in MANETs
## 1 Introduction  
Along with the widespread use of cheaper, smaller and more powerful wireless nodes over the past few years, mobile ad hoc networks (MANETs) have received much attention, making it one of the most promising areas of wireless network development [1; 2]. MANET is a self-organizing, dynamic, infrastructure-less network consisting of a set of wireless nodes that communicate with one another over one or more connections or hops without the need of a central authority [3]. In a MANET, each and every node can function both as a terminal node and as a router, meaning that each node could generate its own traffic while receiving data packets from other nodes and forwarding them to the neighboring nodes. MANETs can be deployed quickly and easily, making them very suitable for applications such as environmental monitoring, military surveillance, disaster rescue, etc. [4; 5]. Quality of Service (QoS) routing is a necessary function in MANETs. In addition to finding the routes from a source to a destination, QoS routing also needs to ensure end-to-end quality, usually in terms of bandwidth or delay [6]. A major challenge for MANETs is the design of a secure and efficient routing protocol that can also ensure the overall quality of service during the routing process as MANET nodes communicate with each other only when they are located within the communication range of each other. When the receiver is far away from the transmitter, i.e., the destination is out of the transmission range of the transmitter, the dynamic nature of MANETs makes it difficult to ensure QoSsince the node-to-node channel and link quality changes dynamically which may result infrequent link failures and cause nodes to make connections with other nodes [7; 8]. Another important issue in MANETs is security since malicious nodes can deliberately misbehave so that packet contents can be altered and packet routing to the desired destinations can be disrupted, lowering packet delivery ratio as well as reliability [9]. Security and trust are correlated with each other. In trust-based security, when trust level increases, so do the access privilege for security protection. In MANETs, trust can be defined based on \"the closeness of the relationships between entities that participate in a protocol interaction\". There are generally two types of trust: social trust and QoS trust with social trust being obtained based on social relationships, e.g., friendship, honesty, privacy and intimacy while QoS trust being obtained based on competency, reliability, experience, number of packets forwarded, etc. [10]. There have already been some proposals for securing the process of routing in MANETs. Although cryptographic techniques have been widely used in routing to protect routing information from being tinkered by the adversary, such an approach may not be practical for real MANETs due to heavy computational overhead and lack of capability of spotting attacking nodes given the high mobility of MANETs where nodes continuously join and leave the networks [11]. Introducing \"trust\" into such a hostile environment can help nodes observe and predict the behavior of neighboring nodes in an efficient manner. The notion of trust is very useful in a highly dynamic environment where nodes need to depend upon each other to accomplish their common goals [12; 13; 14]. Trust-based routing has been considered as an effective measure to deal with security threats caused by malicious nodes through detecting and isolating untrusted nodes in MANETs [15; 16]. In this paper, we propose a new and efficient trust-based secure QoS routing scheme (TSQRS) which combines social trust and QoS trust. The proposed scheme would selecta forwarding node by considering channel quality, link quality and residual energy in order to establish an optimal path in a very dynamic environment and detect intrusions by using the trust of neighboring nodes to mitigate threats by nodes misbehave in packet forwarding during the routing process.