TAODV: A Trusted AODV Routing Protocol for MANET Li Xiaoqi, GiGi March 22, 2004

2 Outline  Introduction  Framework of Truman (TRUsted MANETs)  Trust model for Truman  Routing operations in Truman  Analysis  Conclusion and future work

3 Introduction  Mobile Ad Hoc Networks (MANETs) No fixed infrastructure Self-organized multi-hop routing among nodes Nodes with high mobility Underlying wireless communication medium Frequent link layer errors Vulnerable to kinds of attacks

4 Applications of MANETs  Personal area networking  Meeting rooms  Disaster relief  Battlefield operations  High Security Requirements

5 Previous Security Solutions for MANET  Secure routing protocols may perform digital signature authentication at each routing message huge overhead  Key management mechanisms usually need a super-trusted third-party to issue certificates destroy the self-organization nature of MANETs

6 Basic Idea of Truman  A secure routing protocol for MANETs Make use of trust relationships among nodes Design a trust model derived from subjective logic Need not sign and verify digital signature at each routing message  Cooperate with a self-organized key management mechanism, such as some threshold solutions More scalable and robust

7 Framework of Truman

8 Review of Our Trust Model  Use Opinion to represent trust  Discounting Combination: Combine trusts along one path  Consensus Combination: Combine trusts from several paths  Mapping from evidence space to opinion space: p : positive evidences n : negative evidences

9 Routing Operations in Truman  Trust Recommendation  Route Table Extension  Trust Judgement  Trust Update  Routing Messages Extensions  Trusted Routing Discovery

10 Trust Judgement b – belief d – disbelief u – uncertainty 0.5 – threshold bduActions >0.5Request and verify digital signature >0.5Distrust a node till next certificate renewal >0.5Trust a node and continue routing ≤0.5 Request and verify digital signature

11 Trust Update  Update trust from local evidences Successful Communication  Positive events: p++ Failed Communication  Negative events: n++  Update trust from trust combination Combination from different recommendations  Trust update algorithm T=WeTe+WcTc Usually We>Wc  Update fashion Periodical update if high packets frequency On-demand update if lower packets frequency

12 Routing Messages Extensions  Add such fields into original routing messages Trust information, or Digital signature information  RREQ  TRREQ  RREP  TRREP  Message structure: {original routing information, trust information/signature information}

13 Trusted Routing Discovery: Scenario I-Beginning of Truman  Pre-operations: Each node in this network has generated its own {secret, public} key pair and obtained the public keys of other nodes for further usage of digital signature.  Each node ’ s opinion towards others is (0,0,1), which means total uncertainty of other nodes ’ trustworthiness.

14 Trusted Routing Discovery: Scenario I-Beginning of Truman (con ’ d)  A broadcasts RREQ to discover C  B is uncertain about A  request A to sign itself  A unicast {RREQ} A  B verifies it using P A. If pass, broadcast {RREQ} B  C has P B, verify it and reply {RREP} C  B has P C, verify it and forward {RREP} B  A has P B, verify it and begin data communication

15  During the initialization period, nodes perform digital signing and verification at each routing message  If a node A has passed B ’ s verification, B will update its local route table (route path and trust value) in a certain update fashion.  After first routing communication, the opinions are all changed to (0.33,0,0.67)  Still high computation overhead in the beginning. Trusted Routing Discovery: Scenario I-Beginning of Truman (con ’ d)

16 Trusted Routing Discovery: Scenario II-A Stable Truman S N1 N2 D

17 Performance Analysis  Communication overheads can be sharply reduced by avoiding signature generation and verification at each routing message.  Bandwidth overheads can be largely reduced because of replacing 1024/2048 bit signatures to simple trust values.

18 Security Analysis  If no misbehavior, trust value will keep increasing.  If an external malicious node, it will at once be denied due to not providing valid signature.  We only consider to prevent external attacks.  Internal attacks can be eased through certificates renewal.

19 Conclusion and Future Work  Truman is a trusted MANET which employs two types of security solutions A trusted routing protocol A self-organized key management mechanism  Light computation overheads and a certain security level guarantee.  Perform simulation to proof it.

Q&A Thank You!