1. Secure Neighbor Discovery in Wireless Networks Marcin Poturalski, Panos Papadimitratos, Jean-Pierre Hubaux 1

2. Neighbor Discovery (ND) “Who are my neighbors?” In wireless networks: “Can I communicate directly with B?” Fundamental Building Block 2

3. Neighbor Discovery: Routing in ad-hoc networks C A 3 B

4. Naïve Neighbor Discovery A B “A: Hello” 4 A is a neighbor

5. Naïve ND: relay attack C B A “A: Hello” 5 A is a neighbor “A: Hello” PHY preamble… MAC A …… IP A …“A:Hello”…… PHY preamble… MAC A …… IP A …“A:Hello”……

6. Routing in ad-hoc networks: Violation of ND 6 B A C D M

7. 7

8. ND is an important and fragile building block Secure ND protocols have been proposed – Distance Bounding Does not quite solve the problem… To what extent is secure ND possible? 8

9. Outline Model of wireless networks – language: set theory, 1 st order logic Specification of ND Investigate two classes of protocols: – Time-based (T-protocols) – Time- and Location-based (TL-protocols) Results: – T-protocol ND impossibility (general case) – T-protocol solving ND (restricted case) – TL-protocol solving ND (general case) 9

10. Model 10

11. Traces and events Trace is a set of events 11 A B C

12. SS  S,P Feasible traces System execution: feasible trace Traces feasible with respect to: - setting S - protocol P - adversary A 12  S,P,A 

13. Setting 13 { A, B, C, D, E, F, G, H } ……… H A C B D G F E

14. Trace  feasible wrt setting S Causal and timely message exchange A B 14 v – signal propagation speed

15. Trace  feasible wrt setting S Causal and timely message exchange 15

16. Local trace 16 A B

17. 17 Local view

18. Protocol 18 Actions:

19. 19 Correct nodes follow the protocol Trace  feasible wrt protocol

20. Trace  feasible wrt adversary 20 Adversarial nodes can only relay messages, with minimum delay A

21. 21 Neighbor Discovery Specification

22. Neighbor Discovery specification 1)Discovered neighbors are actual neighbors 2)It is possible to discover neighbors 22 Protocol P solves Neighbor Discovery for adversary A if

23. Neighbor Discovery specification 1)Discovered neighbors are actual neighbors 2)It is possible to discover neighbors 23 Protocol P solves Neighbor Discovery for adversary A if in the ND range R … 2-party ND

24. Results T-protocol ND impossibility (general case) T-protocol solving ND (restricted case) TL-protocol solving ND (general case) 24

25. Results T-protocol ND impossibility (general case) T-protocol solving ND (restricted case) TL-protocol solving ND (general case) 25

26. T-protocol impossibility 26 No T-protocol can solve Neighbor Discovery for adversary if Proof (sketch): Any T-protocol P which satisfies ND 2 cannot satisfy ND 1

27. T-protocol impossibility 27 A B C A B

28. T-protocol impossibility 28 A B

29. T-protocol impossibility 29 A B A B C

30. T-protocol impossibility Trace  b is feasible in S b A declares B a neighbor in  b A and B are not neighbors in S b ND 1 is violated 30 A B C C A B

31. Results T-protocol ND impossibility (general case) T-protocol solving ND (restricted case) TL-protocol solving ND (general case) 31

32. Temporal packet leash: T-protocol solving ND 32

33. Results T-protocol ND impossibility (general case) T-protocol solving ND (restricted case) TL-protocol solving ND (general case) 33

34. TL-protocol solving ND “Geo-Temporal” packet leash: 34

35. Conclusion Investigation of Neighbor Discovery in wireless networks for two general classes of protocols T-protocols can solve ND iff TL-protocols can solve ND if 35

36. Conclusion Problems with proposed protocols: – require synchronized clocks – require very accurate time measurements – require line-of-sight communication (TL) – require secure location (TL) 36

37. Future work Reasoning about a wider range of protocols – e.g. Challenge-Response schemes Multi-party ND? Moving closer to the physical layer – ? 37