TAODV: A Trust Model Based Routing Protocol for Secure Ad Hoc Networks

1. TAODV: A Trust Model Based Routing Protocol for Secure Ad Hoc Networks Li Xiaoqi, GiGi October 28, 2003

2. Outline • Introduction • Background: Subjective logic and AODV • Framework of TAODV • Trust model for TAODV • Routing operations in TAODV • Analysis • Conclusion and future work CSE Dept. of CUHK

3. Introduction to MANETs • Mobile Ad Hoc Networks (MANETs) • No fixed infrastructure • Self-organized routing • Prone to be unstable and insecure • Previous Secure Solutions for MANETs • Require each node to testify itself by showing its digital signature at all times • Need a super-trusted third-party to provide authentication CSE Dept. of CUHK

4. Introduction to TAODV • Make use of trust relationships among nodes • Need not request and verify signature at each time of communication, just like human society • TAODV: a secure routing protocol based on trust model for MANET CSE Dept. of CUHK

5. Background: Subjective Logic • Subjective logic • Represent trust relationship formally • Define how to combine different trust information together • Map all kinds of evidences to trust representation space • We derive our trust model for TAODV from subjective logic CSE Dept. of CUHK

6. Background: AODV • AODV • Ad Hoc On-Demand Distance Vector Routing Protocol for MANETs • Two main routing messages: • RREQ: Routing REQuest • RREP: Routing REPly • We extend AODV by adding trust information into its routing messages CSE Dept. of CUHK

7. Framework of TAODV CSE Dept. of CUHK

8. Trust Model for TAODV: Representation of trust • Use Opinion to represent trust: • A three-dimensional metric • -- Probability of node A believing in node B • -- Probability of node A disbelieving in node B • -- Probability of node A’s uncertainty about B CSE Dept. of CUHK

9. Trust Model for TAODV: Combination of trust • Discounting Combination: • Combine trusts along one path • Combine • Consensus Combination: • Combine trusts from several paths • Combine CSE Dept. of CUHK

10. Trust Model for TAODV: Mapping from evidences to opinion space • Mapping function: • p : positive evidences • n : negative evidences CSE Dept. of CUHK

11. Routing Operations in TAODV • Trust Recommendation • Trust Judgement • Route Table Extension • Trust Update • Routing Messages Extensions • Trusted Routing Discovery CSE Dept. of CUHK

12. Trust Recommendation • Exchange trust information • Two types of messages: • TREQ: Trust REQuest • TREP: Trust REPly • Message structure: CSE Dept. of CUHK

13. Message Structures of TREQ & TREP TREP TREQ CSE Dept. of CUHK

14. Trust Judgement b – belief d – disbelief u – uncertainty 0.5 – threshold CSE Dept. of CUHK

15. Route Table Extension • Add three fields into original route table • Positive events • Negative events • Opinion • New route table format CSE Dept. of CUHK

16. Trust Update • Update of Evidences • Successful Communication Positive events: p++ • Failed Communication Negative events: n++ • Update of opinion • Mapping from evidence space • Combination from different recommendations • Update fashion • Periodical update if high packets frequency • On-demand update if lower packets frequency CSE Dept. of CUHK

17. Routing Messages Extensions • Add trust information into original AODV routing messages • RREQ  TRREQ • RREP  TRREP • Message structure: CSE Dept. of CUHK

18. Message Structures of TRREQ & TRREP TRREP TRREQ CSE Dept. of CUHK

19. N1 N3 TRREQ TRREQ S N D N2 N4 Trusted Routing Discovery • N receives TRREQ from N1. It will then perform such behaviors as follows: • Broadcast TREQ to request N1’s opinions • Obtain trust recommendation from N2, N3, N4: • Combine these three opinions together into • Judge the next behavior using trust judgment criteria CSE Dept. of CUHK N receives TRREQ from N1. It will performs such behaviors:

20. N1 N3 TRREQ TRREQ TRREQ TRREP TRREP S N D TRREQ TRREQ N2 N4 Trusted Routing Discovery • If uncertainty>threshold, N requests and verifies N1’s signature • If N1 passes trust authentication or signature authentication, N will rebroadcast TRREQ • If N1 does not pass any authentication, N will not trust N1 and drop this TRREQ • Update the value of opinion using trust update rules CSE Dept. of CUHK

21. Analysis • Computation overheads of each set of authentication operations • Cost of each set of trust operations is O(162v) (v is the no. of average neighbors) • Cost of each set of signature operations is O(k3) (k is the length of signature) CSE Dept. of CUHK

22. Analysis (con’d) • Number of authentication operations when given a certain traffic volume. E.g.: n routing messages • No. of signature operations: n • No. of trust operations: • t – average packets interval • e – trust expiry time • U will never be larger than n CSE Dept. of CUHK

23. Analysis (con’d) • Security • Combination of trust authentication and signature authentication  secure • Combination of different recommendations  objective • Customization of trust threshold  flexible CSE Dept. of CUHK

24. Conclusion and Future Work • TAODV is a secure routing protocol with • Less computation overheads • Flexible security levels • Optimize trusted routing discovery algorithm • Establish fast response mechanism when being attacked • Perform detailed simulation evaluation CSE Dept. of CUHK

25. Q&A Thank You!