Castor: Scalable Secure Routing for Ad Hoc Networks

1. Castor: Scalable Secure Routing for Ad Hoc Networks WojciechGaluba, Panos Papadimitratos, Marcin Poturalski, Karl Aberer EPFL, Switzerland ZoranDespotovic, Wolfgang KellererDocomo Euro-Labs, Munich, Germany

2. Ad-hoc network routing challenges source destination

3. Ad-hoc network routing challenges source destination

4. Ad-hoc network routing challenges source destination

5. Scale Mobility ? Security

6. Secure route discovery Castor Secure data transmission • Evaluates routes • Needs route redundancy Continuously-Adapting Secure Topology-Oblivious Routing Provides routes Avoids compromised nodes

7. Topology-obliviousness • Nodes only aware of their neighbors • No routing information exchange • no routes included in control traffic • no routing table fragments exchanged

8. Flows instead of destinations d1 s1 d2 s2 • In-network state is maintained per-flow • not per-destination • Flow isolation  crucial for security

9. Castor – basic operation source destination PKTscontain the data payload ACKs follow the reverse path of PKTs

10. Local learning from failures v3 per-flow per-neighbor reliability estimator - - + + + v2 v1 v4 + + • Locality: each node only aware of its neighborhood • Autonomy: each node routes independently

11. Broadcast as a fallback v3 - - - v1 v2 v4 • Autonomy: nodes independently decide wether to broadcast or unicast

12. Initial PKT flood source destination No reliability history  each node decides to broadcast the PKT ACKs are broadcasted back

13. Routing around failures source destination • Failure  ACKs stop returning • Local repair: • on failure some nodes broadcast, most still unicast • alternative route discovered without network-wide flood

14. Castor is failure agnostic • Same recovery mechanism good for: • Malicious PKT or ACK dropping • Links broken by mobility • Wider-area outages (e.g. jamming) • Wormholes and tunnels

15. Trust model d1 s1 d2 s2 • Untrusted cloud of intermediate nodes • Security associations: • Source to destination • Neighbor to neighbor

16. Crucial property: flow state isolation v2 v5 v1 v4 v3 Routing state at v1: Isolate in-network states for the two flows Otherwise malicious flows could disrupt the benign flows

17. Ensuring flow isolation • Flow authentication • Nodes can recognize PKTs belonging to the same flow • Only source can generate the next PKT • ACK authentication • Nodes can match ACKs to PKTs • Only destination can generate correct ACK • Achieved without public-key crypto

18. Evaluation 1Mbps 802.11b MAC 3 km x 3 km plane 1-20 m/s random waypoint mobility 5 flows, 4 packets/s, 100 nodes

19. Blackhole attack: adversary drops data packets • not control traffic

20. Bandwidth utilization under blackhole attack

21. Wormhole drops data packets, no mobility Complete recovery from wormholes

22. Mobility, 20% of balckholes • Increasing the network size Scalability

23. Summary • Simple PKT-ACK messaging • flow-control-ready • applicable to other networks than MANETs • Scalability • No routing information exchanged • Local repair, few network-wide floods • Fast adaptation • Security • Failure agnosticism • Flow state isolation