1. SeCoWiNet 2007 FAMIC Fast Authentication and Message Integrity Check in Vehicular Communications Nikodin Ristanovic Papadimitratos Panos George Theodorakopoulos Jean-Pierre Hubaux

2. 7/13/2015 2 Intro IVC – Inter-Vehicle Communication expected to play a significant role in VNs Multi-hop communication difficult to avoid (both 802.11 and IEEE 1609 suite of WAVE standards designed for short range communication) OUR FOCUS: end-to-end delay of messages; more precisely the component of the delay caused by message processing in intermediate nodes

3. 7/13/2015 3 Quick reminder An existing architecture that we build upon Provides authenticated and integer communication Tries to protect privacy

4. 7/13/2015 4 Security costs eCrypt project ppc 32 533MHz, Motorola powerPC G4 7410 Microsoft Windows Mobile for Automotive 1.0 Expected frequency of safety messages (every 300ms) Many of these messages not interesting for receiving node

5. 7/13/2015 5 Motivating example Congestion notification application [17],[18] Vehicles expected to relay messages for each other – Observation 1) Limited scope of the adversaries – Observation 2) An adversary = a non- legitimate node sending forged messages

6. 7/13/2015 6 Our Idea Reverse the order of operations! 1 2

7. 7/13/2015 7 The scheme - FAMIC Quick Filter – Am I interested in this message ? Check integrity of the message, authenticate OK Use and/or Forward … Queue reduce/ increase check rate Background check Forward Alert/OK ToMTime…Source loc.Dest. loc.Sender’s sign.Sender’s PKCA’s cert. of PK Yes No “Relaxed” vs. “Check all” mode

8. 7/13/2015 8 Security issues Performance improved, but certain security risks introduced Some messages are relayed without prior authentication and integrity check DoS attack –The goal: increase the amount of forged traffic in the network (i. e. degrade the whole service)

9. 7/13/2015 9 The game in strategic form - decides if the message receives is going to be forged or not - decides whether to check the received message or not (1) (2)

10. 7/13/2015 10 Best response functions For a finite strategy space (i.e. for so called finite games), the payoff of each player to profile is given by: - the profile; - the pure strategies of the players (3) (4) (5) - probability that a received message is forged - probability of checking the message that is going to be relayed

11. 7/13/2015 11 The result (6) (7)

12. 7/13/2015 12 Interpretation (8) (9) (11) (10) Mixed strategy equilibrium: Example:

13. 7/13/2015 13 Performance evaluation We consider the scheme with only two modes of operation: –“relaxed” mode of operation –“check all” mode of operation Performance improved over 40% under very realistic assumptions Up to 80% under some stronger assumptions Very good responsiveness even when the adversary tries to “keep a low profile”

14. 7/13/2015 14 Example 10% of the network under attack, on average 10% checking rate in “relaxed” mode of operation (this concerns the messages that are only relayed) Legitimate node 10% of the time in “relaxed” mode of operation 90% of the time in “check all” mode of operation (12) - the average checking rate of the messages that are only supposed to be relayed

15. 7/13/2015 15 Reduced security costs 01020406080100 00.190.280.460.640.821 - the average checking rate of the messages that are only supposed to be relayed - the percentage of the network under attack (on average)

16. 7/13/2015 16 Performance boost Previous assumptions + 50% of the received messages have the receiving node as destination; the other 50% are relayed; 20% of the received messages have the receiving node as destination; the other 80% are relayed; - the average checking rate of the messages that are only supposed to be relayed - the percentage of the network under attack (on average)

17. 7/13/2015 17 Responsiveness 1Mbps – incoming traffic per node 1.5kB – message size 83 messages/s 10% nodes are adversaries 0.9 – the probability that a received message is valid (13) (14) - time needed to detect the threat and switch from “relaxed” to “check all” mode of operation

18. 7/13/2015 18 Triggering times - time needed to detect the threat and switch from “relaxed” to “check all” mode of operation - the percentage of fake messages in the network Quick reaction to the presence of an adversary means that the injected forged messages are kept locally

19. 7/13/2015 19 Discussion and related work The same approach can be applied to messages that ARE destined for the node Advanced classification of messages – ephemeral trust M. Raya, P. Papadimitratos, J.-P. Hubaux –ECDSA, NTRU – key size vs. delay –Correlation – ignoring the redundant messages (safety message broadcast frequency – typically, every 300ms)

20. 7/13/2015 20 Conclusion Reactive vs. proactive approach We question the necessity of strong security measures under certain assumptions We show that for a group of applications that adhere to certain observations, the increase in performance can be significant We believe it is worth further investigation

21. 7/13/2015 21 References (1) M. Raya, P. Papadimitratos, and J.-P. Hubaux, Securing Vehicular Communications, In IEEE Wireless Communications Magazine, Special Issue on Inter-Vehicular Communications, October 2006. F. Dotzer, T. Kosch, M. Strassberger, Classification for traffic related inter-vehicle messaging, 5th IEEE International Conference on ITS Telecommunications, Brest, France, June 27-29, 2005. Naoki Shibata, Takashi Terauchi, Tomoya Kitani, Keiichi Yasumoto, Minoru Ito, Teruo Higashino. A Method for Sharing Traffic Jam Information using Inter-Vehicle Communication. Mobile and Ubiquitous Systems: Networking & Services, 2006 Third Annual International Conference http://www.ecrypt.eu.org/ebats/

22. 7/13/2015 22 References (2) M. Mauve, A. Widmer, H. Hartenstein, A Survey on Position- Based Routing in Mobile Ad-Hoc Networks in Network, IEEE, Nov/Dec 2001 Windows Mobile for Automotive 1.0: http://www.microsoft.com/windowsautomotive/wma/default.m spx http://www.microsoft.com/windowsautomotive/wma/default.m spx "Security and Cooperation in Wireless Networks" by Levente Buttyan and Jean-Pierre Hubaux "Security and Cooperation in Wireless Networks" Alaeddine El Fawal, Jean-Yves Le Boudec, Kave Salamatian.Self-Limiting Epidemic Forwarding. LCA-REPORT- 2006-126, 2006

23. 7/13/2015 23 Questions? Answers ? Q&A