SGOR: Secure and scalable geographic opportunistic routing with received signal strength in WSNs

Abstract

Wireless sensor networks (WSNs) are inherently susceptible to attacks as malicious nodes can disrupt the communication from any other node to the sink. To address a wide range of attacks, we propose a novel and comprehensive approach called Secure and Scalable Geographic Opportunistic Routing with received signal strength (SGOR), satisfying the requirements of both security and scalability in WSNs. Unlike most of previous secure protocols relying on infrastructure like anchor nodes, a distributed location verification algorithm is presented to utilize the received signal strength to address the location spoofing attack. As one of opportunistic geographic routings, SGOR provides the property of robustness by taking full advantage of the broadcast nature of wireless channels, and scalability for being inherited from geographic routing. Moreover, an ambient-sensitive trust model is proposed to defend against more kinds of attackers in SGOR. The theoretical results are given to demonstrate the effectiveness and robustness of SGOR to survive more severe attacks. In extensive simulations, we compare SGOR with four other representative protocols. The results show that SGOR achieves about two times higher packet delivery rate with acceptable overhead, particularly in large and highly hostile networks.

Introduction

Wireless sensor networks (WSNs) have been extensively researched because of the significant advantage brought by infrastructure-less and multi-hop transmissions. Many security issues [1], [2], [3] arise from the nature of such networks, but traditional security mechanisms cannot be applied directly to protect WSNs for their resource constraints. In the case of WSNs, the proposed protocol is expected to be scalable with a large number of nodes and has security protection with minimal resource consumption.

Network routing is an essential service for communication in wireless ad hoc networks and sensor networks. There are many topology based routing protocols such as DSDV [4], AODV [5] and ZRP [6]. However, all of them are potentially the targets of different attacks in the open network environment, and quite vulnerable in the process of route discovery. An adversary may employ various methods to undermine a well-established path so that the data packets would never reach the destination or sink node. Geographic routing (GR), such as GPSR [7], is an attractive approach for sensor networks as no end-to-end route is determined before data transmission. Moreover, each node in the GR only keeps the local one-hop connectivity leading to high efficiency and scalability.

In the case of GR, Karlof et al. [8] discussed the possible routing disruption attacks and countermeasures. They pointed out that location spoofing attack can seriously disrupt a GR protocol as no supervision mechanism was designed to securely verify the node at the location that it claimed. An attacker may exploit this vulnerability to attract sensor nodes to route through it, and then degrade or even deny communication by self-organizing operations. Unfortunately, we cannot use traditional cryptographic methods to prevent this type of attack. Prior works [9], [10] suggest using a number of trusted anchor nodes that cover all the sensor nodes to verify the node’s position. However, relying on such a framework may not be feasible for all types of applications. Our SGOR is distributed and makes use of the Received Signal Strength (RSS) in the physical layer to detect attacks correlated to location information. With the assistance of other sensor nodes, the proposed location verification algorithm prevents a range of location-related attacks on routing by offering nodes the location with possibility.

Furthermore, there are other types of attacks such as dropping attacks. Secure routing protocol should guarantee acceptable packet delivery rate against all the possible adversaries. A lot of studies show that multicast routing provides the redundancy to enhance the robustness in ad hoc networks [11]. Due to the broadcast nature of wireless channel, data packet transmission can be overheard by multiple receivers. If multiple forwarding nodes (or candidates) are selected for the packet, transmission of the packet is not interrupted as long as one candidate successfully relays it. This routing mechanism called opportunistic routing has been proposed in [12], [13], and is deployed in our protocol. In highly volatile networks, the robustness of SGOR can be significantly improved as more candidates are used as backups. Moreover, an ambient-sensitive trust model is integrated in our effective routing metric to copy with the malicious behaviors initiated by the adversaries. Therefore, as per-hop packet transmission in the wireless channel can be instantly controlled by the sender, SGOR defends against a wide range of attacks. Our extensive comparative evolution shows that SGOR outperforms four other protocols (GPSR, ZRP, SEAD [14] and SIGF [15]) with significant advantages. SGOR achieves up to more than 60% packet delivery rate (PDR) when all nodes become gray holes which maliciously drop packets with the possibility of 0.6, about twice the other protocols.

In this paper, we propose a novel routing strategy SGOR, which is an opportunistic routing with the RSS measurements to demonstrate the robustness against various attacks. The main contributions of this paper are summarized as follows:

• We propose a secure and scalable geographic opportunistic routing protocol, which can be deployed without costly Public Key Infrastructure and can resist a wide range of attacks.

• Location spoofing attack is detected by cooperated sensor nodes by means of RSS measurements in physical layer. Either the majority voting scheme or prediction scheme is integrated into to address location spoofing attack. We analyze the effectiveness of both schemes in face of different attack intensity.

• We develop an ambient-sensitive trust model to response to attacks in the routing, combining the indirect trust model and direct trust model. The novelty of the indirect trust model mainly lies in sensor nodes’ cooperative location verification.

• We use the conception of more candidates for routing to provide redundancy and randomness to significantly enhance the resilience in the hostile environments. We analyze the effect of packets dropping attack on packet delivery rate, and then explain the results brought by the opportunistic routing.

• Finally, we evaluate the performance of SGOR through security analysis and extensive simulations. It demonstrates that SGOR achieves excellent performance with acceptable overhead under various attacks.

In the rest of this paper, we first describe the related work in Section 2. Section 3 defines the network and security model. We present our protocol in Section 4. The effectiveness, robustness and security analysis of SGOR are performed in Section 5. In Section 6, the performance of the proposed scheme is evaluated. Finally, we conclude our paper in Section 7.