1. KAIS T AO2P: Ad Hoc On-Demand Position- Based Private Routing Protocol IEEE Transactions on Mobile Computing Vol.4, No. 3, May 2005 Xiaoxin Wu 2006. 11. 14. Presented by JooBeom Yun

2. 2 / 18 Security architecture in a multi-hop mesh network Contents Introduction Related Research AO2P Routing Algorithm Position Management AO2P Routing Protocol Receiver Classification AO2P hrep Contention Mechanism Communication Anonymity and Privacy Enhancement AO2P Performance Evaluation Delay for AO2P Next Hop Searching Routing Failure and Impact of Inaccurate Position Information Illustrative Data and Observations Analysis Results Simulation Results Conclusions and Future Works

3. 3 / 18 Security architecture in a multi-hop mesh network Introduction (1/2) Protecting personal privacy is a prime concern. User anonymity Disclose node identity Routing algorithms - AODV[1], DSR[2], DSDV[3] The privacy preservation approaches do not directly extend to ad hoc networks. Broadcast or multicast K-anonymity algorithm Anonymity solutions based on trusted third party Previous geographic or position-based routing algorithms Does not guarantee node anonymity Extensive position information exposure

4. 4 / 18 Security architecture in a multi-hop mesh network Introduction (2/2) AO2P is proposed A position-based ad hoc routing algorithm Does not rely on the local position information exchange Receiver contention channel access mechanism Pseudo ID( H(position+time) ) and temporary MAC address AO2P mitigates the attacks on node anonymity from both external and internal attackers. The contributions of this paper The design and routing performance evaluation for the proposed anonymous positioning routing algorithm.

5. 5 / 18 Security architecture in a multi-hop mesh network Related Research ANODR[16] Pseudorandom numbers are used as temporary ID Each node only knows the numbers from previous hop and next hop. GPSR (greedy perimeter stateless routing) [17] A packet forwarded to the next hop closest to the destination May not find the optimum route Requires much more position information Position availability GPS (Global Positioning System) Ad hoc/cellular integrated environment Out-of-band solution - Paging or short message service In-band – VHR(Virtual Home Region)

6. 6 / 18 Security architecture in a multi-hop mesh network AO2P Routing Algorithm Position Management AO2P Routing Protocol Receiver Classification AO2P hrep Contention Mechanism Communication Anonymity and Privacy Enhancement

7. 7 / 18 Security architecture in a multi-hop mesh network Position Management Proposed DISPOSER(VHR-based distributed secure position service) [24] Each node has a VHR (Virtual Home Region). Node send a position request acquiring a node’s position. Update position – move distance exceeds a threshold value DISPOSER enhances position security. Only a small number of trusted nodes can act as position servers. Tracing a target node (continuous sending) is prevented The source gets the position, the time, an authentication code of the destination.

8. 8 / 18 Security architecture in a multi-hop mesh network AO2P Routing Protocol (1/4) A source discovers the route through the delivery of a routing request to its destination. Process for finding the route Generate a pseudo ID and a temporary MAC address Send out a routing request (rreq) message The position of the destination, the distance, source pseudo ID, TTL Challenge message Receivers receive the rreq Receivers send out a hop reply(hrep) message (receiver-contention mechanism) The source replies with a confirm(cnfm) message Next hop replies to this message with an ack. The source saves the pseudo ID and the temporary MAC address.

9. 9 / 18 Security architecture in a multi-hop mesh network AO2P Routing Protocol (2/4)

10. 10 / 18 Security architecture in a multi-hop mesh network AO2P Routing Protocol (3/4) After receiving the cnfm, the next-hop receiver becomes a sender. The searching of the next hop is repeated until the destination receives the rreq. After receiving the cnfm from its previous hop, the destination sends a routing reply(rrep) message(with encrypted result) to the source. The source finds out whether it reaches the right destination.

11. 11 / 18 Security architecture in a multi-hop mesh network AO2P Routing Protocol (4/4) A route discovery failure A sender cannot find a legitimate next hop Destination mobility  a routing discovery failure report sent back to the source. restart After a route is built up, data packets are delivered the pseudo ID and temporary MAC address pairs in the routing tables. Routing maintenance mechanism A node will generate a pair of a pseudo ID and temporary MAC address only when it receives a rreq.

12. 12 / 18 Security architecture in a multi-hop mesh network Receiver Classification (1/2) A receiver determines its node class by finding Δd All nodes divided into four classes Class 1 : Δd >= 2d (highest) Class 2 : d <= Δd < 2d Class 3 : 0 <= Δd < d Class 4 : Δd < 0 Nodes of class 1,2,3 will contend to be legitimate receivers. The node classification scheme is used only for simplicity of presentation and will be used in the rest of the paper. Node density, signal quality, power of a node, node mobility

13. 13 / 18 Security architecture in a multi-hop mesh network Receiver Classification (2/2)

14. 14 / 18 Security architecture in a multi-hop mesh network AO2P hrep Contention Mechanism(1/3) EY-NPMA (Elimination Yield-Non-preemptive Priority Multiple Access) Receiver-contention mechanism Reason for using EY-NPMA is a class-based channel access mechanism The probability of a successful transmission is very high EY-NPMA has been widely used and tested The hrep contention phase of AO2P is divided into three phases Prioritization phase Elimination phase Yield phase

15. 15 / 18 Security architecture in a multi-hop mesh network AO2P hrep Contention Mechanism(2/3) Prioritization phase A number of slots, the same as the number of different priority classes The receivers with the highest channel access priority Elimination phase The receivers transmitting the longest series of bursts will survive. Yield phase A receiver listens to the channel and, if the channel is sensed idle during the yield listening interval, it will send out the hrep. If a hrep collision occurs, the sender will resend the rreq.

16. 16 / 18 Security architecture in a multi-hop mesh network AO2P hrep Contention Mechanism(3/3)

17. 17 / 18 Security architecture in a multi-hop mesh network Communication Anonymity & Privacy Enhancement In AO2P, source and destination are anonymous Intermediate forwarders also don’t expose any information Destination anonymity (from eavesdroppers) A reference point instead of the real position of the destination R-AO2P (AO2P with reference point) The reference point is on the extended line from the sender to the destination Generally, a node closer to the reference point is also closer to the destination

18. 18 / 18 Security architecture in a multi-hop mesh network Communication Anonymity & Privacy Enhancement

19. 19 / 18 Security architecture in a multi-hop mesh network Communication Anonymity & Privacy Enhancement R-AO2P The next hop obtain the position of the destination from the sender The position is encrypted by a Diffie-Hellman key After receiving the position of the destination, the next hop can generate a reference point at the extended line Sends out a rreq

20. 20 / 18 Security architecture in a multi-hop mesh network AO2P Performance Evaluation They first analyze the hrep average delay. Based on this delay, the average time needed for a successful next hop determination is calculated. Analysis for the probability of a route discovery failure under node distributions and position accuracy

21. 21 / 18 Security architecture in a multi-hop mesh network Delay for AO2P Next Hop Searching (1/2) Average time for next hop determination when there are n contenders

22. 22 / 18 Security architecture in a multi-hop mesh network Delay for AO2P Next Hop Searching (2/2)

23. 23 / 18 Security architecture in a multi-hop mesh network Routing Failure and Impact of Inaccurate Position Information Relatively large position error (GPS, cellular position) The worst case of how the position error cause a route discovery failure. In R-AO2P, d >> r  The probability of a route discovery failure with and without position error (p1 and p2) are approximately the same.

24. 24 / 18 Security architecture in a multi-hop mesh network Routing Failure and Impact of Inaccurate Position Information

25. 25 / 18 Security architecture in a multi-hop mesh network Illustrative Data and Observations Analysis Results The Average Delay for rreq Transmission Cycle Impact of Position Error Simulation Results Impact of Position Error Impact of Destination Mobility AO2P, R-AO2P, and GPSR Comparisons

26. 26 / 18 Security architecture in a multi-hop mesh network The Average Delay for rreq Transmission Cycle The major parameters are set in HIPERLAN1 standard The number of slots = 5, 12, 9 (prioritization, elimination, yield) Duration time = 7.2µs, 9µs, 7.2µs Synchronization interval = 11µs SIFS = 28µs, DIFS = 128µs Rreq, hrep, cnfm transmitted rate = 1Mb/s Extra physical header = 128 bits Ack length = 240 bits Ack trasmitted rate = 1Mb/s

27. 27 / 18 Security architecture in a multi-hop mesh network The Average Delay for rreq Transmission Cycle

28. 28 / 18 Security architecture in a multi-hop mesh network Impact of Position Error

29. 29 / 18 Security architecture in a multi-hop mesh network Simulation Results Simulation Scenario Network cover – 1,000m X 1,000m Transmission rage – 250m

30. 30 / 18 Security architecture in a multi-hop mesh network Impact of Position Error

31. 31 / 18 Security architecture in a multi-hop mesh network Impact of Destination Mobility

32. 32 / 18 Security architecture in a multi-hop mesh network AO2P, R-AO2P, and GPSR Comparisons

33. 33 / 18 Security architecture in a multi-hop mesh network Conclusions (1/2) Propose a routing algorithm, AO2P, for communication privacy Node position (not identity) is used for route discovery R-AO2P was proposed AO2P and R-AO2P delay is small Only a few milliseconds Evaluate the impact of position error Less significant with high node densities Impact of destination mobility May not necessarily leads to a route discovery failure Less significant with high node densities Compare the routing performance between AO2P/R-AO2P and GPSR

34. 34 / 18 Security architecture in a multi-hop mesh network Conclusions (2/2) AO2P preserves communication privacy without significant routing performance degradation.