Using Directional Antennas to Prevent Wormhole Attacks

Using Directional Antennas to Prevent Wormhole Attacks Lingxuan Hu David Evans Department of Computer Science University of Virginia

Outline • Problem Statement • Background • Protocol • Experiment

Scenario High-power base station Thousands of small, low-powered devices with sensors and actuators, communicating wirelessly

Routing Tree Adapted from Chris Karlof and David Wagner's WSNPA slides

Routing Adapted from Chris Karlof and David Wagner's WSNPA slides

Wormhole Attack • Tunnel packets received in one place of the network and replay them in another place • The attacker can have no key material. All it requires is two transceivers and one high quality out-of-band channel Adapted from Chris Karlof and David Wagner's WSNPA slides

Disrupted Routing • Most packets will be routed to the wormhole • The wormhole can drop packets or more subtly, selectively forward packets to avoid detection Adapted from Chris Karlof and David Wagner's WSNPA slides

Impact of Wormhole — Experiment Base Station at Corner Base Station at Center How many routing paths are disrupted by a single wormhole?

Impact of Wormhole — Result

Possible Solutions • Time • Signal is transmitted at speed of light • Location • Location awareness • Direction • Directional Antennas

Directional Antennas Operation Modes: OmniandDirectional In Omni Mode: Nodes send signals with gain Go In Directional Mode: Capable of sending in specified direction Directional Gain Gd(Gd > Go)

Antenna Model East The model is comprised of N antenna zones. The N zones may collectively cover the entire plane The zones are numbered 1 to N oriented clockwise starting with zone 1 facing east The channel is bidirectional. For, example, if A hears B from zone 1, then B will hear A in zone 4, which is the opposite zone

Simple Neighbor Discovery HELLO | IDA IDN| EKNA (IDA | R | zone(N, A)) R N A A Region Announcement, done through sequential sweeping NA Include nonce and zone information in the message A N Check zone information and send back the nonce

Detecting Wormhole zone (A, B) = 1 Wrong! zone (A, B) = 4 Hello B A

Sophisticated Wormhole zone (A, B) = 1 Yes! zone (A, B) = 1 Hello A B Simple Neighbor Discovery can reduce the chance of successful wormhole attack to 1/6, but it is still unacceptable since a single wormhole can disrupt most routing paths. Possible Solution: Neighborhood coordination

Verification Region v zone (B, A) = 4 zone (B, V) = 5 zone (B, A) = 4 zone (V, A) = 3 • zone (B, A) ≠ zone (B, V) • zone (B, A) ≠ zone (V, A)

Verifier Analysis zone (B, A) = zone (V, A) zone (B, A) = zone (B, V) v v • zone (B, A) ≠ zone (B, V) • zone (B, A) ≠ zone (V, A)

Worawannotai attack A and B are just beyond the transmission range of each other There does have a valid verifier V in this case X simply retransmits messages between A and B, X doesn’t need to retransmit the message of V.

Strict Neighbor Discovery Theorem: In strict neighbor discovery, if distance (A, B) > r, the verification region is empty Strict verification region • zone (B, A) ≠ zone (B, V) • zone (B, A) ≠ zone (V, A) • zone (B, V) can not be both adjacent to • zone (B, A) and adjacent to zone (V, A)

Cost Analysis • Communication Overhead • The typical secure link establishment includes announcement, challenge and response • This protocol adds inquiry, verification and acceptance • Connectivity • Only accept a node as neighbor if it can be verified by at least one verifier, so may prevent some legitimate links from being established

Impact on Connectivity Verified Protocol, Omni density = 3 Strict Protocol, Omni density = 3 For a more typical network with omni density = 10. In verified protocol, 0.5% links are lost and no nodes are disconnected. In strict protocol, 40% links are lost and 0.03% nodes are disconnected.

Node Distance vs Connectivity Strict Protocol Verified Protocol

Impact on Routing • For verified protocol, the routing path length is nearly the same • For strict protocol, the routing path length increases around 20%

Directional Errors Omni density = 3 Omni density = 10 The error is modeled by disorienting nodes by a random angle in [-max, max] The disconnected nodes is little affected The lost links will increases as maximum directional error degree increases

Conclusion • Wormhole attack is a powerful attack that can be conducted without any cryptographic breaks • Directional antennas offers a promising approach to preventing wormhole attacks through neighborhood coordination

Discussion • Design protocols to prevent more powerful wormhole attacks • Or try to prove that some powerful wormhole is unpreventable if no assumption on time synchronization or location awareness is made. • Mitigate replay attacks in other layers (routing, application)

References [1] L. Hu and D. Evans. Using Directional Antennas to Prevent Wormhole Attacks. Network and Distributed System Security Symposium, San Diego, 5-6 February 2004. [2] R. Ramanathan. On the Performance of Beamforming Antennas in Ad Hoc Network. MobiHoc 2001, October 2001. [3] Y. Hu, A. Perrig, and D. Johnson. Packet Leashes: A Defense against Wormhole Attacks in Wireless Ad Hoc Networks. INFOCOM 2003, April 2003. [4] C. Karlof and D. Wagner. Secure Routing in Sensor Networks: Attacks and Countermeasures. First IEEE International Workshop on Sensor Network Protocols and Applications, May, 2003.

Using Directional Antennas to Prevent Wormhole Attacks