AO2P: Ad Hoc On-Demand Position-Based Private Routing Protocol

1. 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. 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 Security architecture in a multi-hop mesh network

3. 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 Security architecture in a multi-hop mesh network

4. 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. Security architecture in a multi-hop mesh network

5. 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) Security architecture in a multi-hop mesh network

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

7. 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. Security architecture in a multi-hop mesh network

8. 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. Security architecture in a multi-hop mesh network

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

10. 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. Security architecture in a multi-hop mesh network

11. 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. Security architecture in a multi-hop mesh network

12. 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 Security architecture in a multi-hop mesh network

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

14. 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 Security architecture in a multi-hop mesh network

15. 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. Security architecture in a multi-hop mesh network

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

17. 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 Security architecture in a multi-hop mesh network

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

19. 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 Security architecture in a multi-hop mesh network

20. 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 Security architecture in a multi-hop mesh network

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

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

23. 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. Security architecture in a multi-hop mesh network

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

25. 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 Security architecture in a multi-hop mesh network

26. 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 Security architecture in a multi-hop mesh network

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

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

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

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

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

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

33. 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 Security architecture in a multi-hop mesh network

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