Securing Virtual Coordinate System Based Routing in Wireless Sensor Networks

Virtual coordinate system (VCS) based routing provides a practical, efficient and scalable means for point-to-point routing in wireless sensor networks. Several VCS-based routing protocols have been proposed in the last few years, all assuming that nodes are cooperative. However, malicious nodes may violate this assumption, making VCS-based routing protocols vulnerable to numerous attacks. Thus, it is critical to provide security mechanisms for these protocols to ensure correct operations in adversarial deployment environments. In this work, we study the security of VCS-based routing protocols. We identify new attacks targeting the accuracy and stability of virtual coordinates that VCS-based routing relies on and propose several defense mechanisms against the identified attacks. We evaluate the impact of the attacks and the effectiveness of our defense mechanisms using a well-known VCS-based routing protocol, BVR. Wireless sensor network designs have evolved in recent years, from primarily focusing on data collection [ l ] to more sophisticated tasks such as data centric storage [2], [3]. Likewise, the requirements for communication protocols have also evolved, from the basic many-toone and one-to-many communications to more sophisticated point-to-point communications. Well-known wireless routing protocols such as AODV [4] and DSR [5] are not appropriate solutions for sensor networks as they do not scale well for large networks and have relatively high overhead. Virtual coordinate system (VCS) based routing protocols have been proposed to overcome these limitations. In such protocols, routing is performed in a greedy manner based on virtual (or logical) coordinates obtained through a virtual coordinate establishment mechanism integrated with the routing protocol or through an external virtual coordinate system. VCSbased routing protocols require only local interactions and minimal state information that does not grow with the size of the network. As a result, such protocols have increased scalability and reduced overhead. In this paper, we study the problem of securing VCSrouting protocols. Like other routing protocols, VCSbased routing protocols are vulnerable to numerous attacks that seek to disturb the routing service by injecting, modifying, replaying or dropping packets. In addition, VCS-based routing protocols depend significantly on the accuracy and stability of the virtual coordinates. Our contributions are: . We identify and analyze new attacks against VCSbased routing protocols that target the virtual coordinates. We refer to the attacks as coordinate injation, dejation, oscillation, and pollution attacks. We show that virtual coordinate accuracy can be significantly influenced by coordinate injution, dejation and pollution attacks while virtual coordinate stability can be influenced by coordinate oscillation attacks. . We evaluate experimentally the impact of the attacks on the accuracy and stability of virtual coordinates and on the routing performance, using a wellknown VCS-based routing protocol, BVR [8]. Our experiments show that coordinate deflation is the most damaging attack, while coordinate inflation creates the least damage. . We propose defense mechanisms against virtual coordinate attacks. Specifically, we use hop-byhop authentication and a novel wormhole detection technique to address coordinate deflation. We introduce a coordinate variance based parent selection mechanism to mitigate coordinate oscillation attacks and a coordinate replication technique to mitigate coordinate pollution attacks. . We demonstrate the effectiveness of the proposed defense and mitigation mechanisms through simulations using an implementation of the BVR protocol in the TOSSIM [lo] simulator. Although several VCS-based routing protocols have The rest of the paper is organized as follows. Secbeen proposed in the last few years [6], [7], [8], [9], there tion I1 provides an overview of the main mechanisms has been little work that investigates the security of such involved in the design of VCS-based routing protocols. protocols. As many applications for wireless sensor netSection I11 presents attacks against the virtual coordiworks require deployment in adversarial environments, it nates. Section IV outlines several defense mechanisms. is critical to provide security mechanisms to make these Section V demonstrates the impact of the attacks and the protocols operate correctly in the presence of attackers. effectiveness of our defense mechanisms using the BVR ar,crisn} tractVirtual e ) tti i t l s. l YeSi t c l i tive. , li i s i ti , i YeSs i toc ls l c s. , i is s t l ti i l e ts. i , YeSs t l if ili t YeSs i li s i c s. i s YeSi t c l,