TAODV: A Trusted AODV Routing Protocol for MANET Li Xiaoqi, GiGi Term Presentation 2004-4-27

Outline Introduction Framework of TAODV Trust model for TAODV Routing operations in TAODV Analyses and simulations Conclusion

Now Comes to: Introduction Framework of TAODV Trust model for TAODV Routing Operations in TAODV Analyses and Simulations Conclusion

Introduction Mobile Ad Hoc Network (MANET) No fixed infrastructure Multi-hop routing by cooperation of nodes in a self-organized way Nodes has high mobility Underlying medium is wireless Frequent link layer errors Vulnerable to kinds of attacks

Routing Protocols for MANET DSR: The Dynamic Source Routing Protocol DSDV: Destination-Sequenced Distance Vector Protocol AODV: Ad Hoc On-Demand Distance Vector Protocol Two main routing messages: RREQ: Routing REQuest RREP: Routing REPly Currently the most popular routing protocols for ad hoc networks include: AODV which stands for ad hoc on demand distance vector protocol DSR: DSDV

 High Security Requirements Applications of MANET  High Security Requirements Personal area networking Meeting rooms Disaster relief Battlefield operations

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

Previous Security Solutions for MANET (con’d) Intrusion detection mechanism Listen, collect and analyze all traffics on each node Huge process overhead Our aim is to design a secure routing protocol, called TAODV (Trusted AODV Routing Protocol), without introducing huge overhead or destroying the self-organization nature of MANET

Now Comes to: Introduction Framework of TAODV Trust model for TAODV Routing Operations in TAODV Analyses and Simulations Conclusion

Main Ideas of TAODV A secure routing protocol for MANET Use trust relationships among nodes for routing Employ a trust model derived from subjective logic Trust calculation is not very time-consuming Need not sign and verify digital signature at each routing message Cooperate with a self-organized key management mechanism such as some threshold solutions We take AODV for example to illustrate our idea

Four Modules of TAODV Basic routing protocol (AODV in this work) Trust model Define the algorithms or rules to combine, judge, and update trust information based on subjective logic Trusted routing protocol Self-organized key management mechanism generate a {secret, public} key pair for each node and distribute public keys in a secure self-organized way A pre-requisition, will not discuss it in this presentation

Module of Trusted Routing Protocol Include operations of trust recommendation trust combination trust judgement trust update signature authentication trust authentication

Framework of TAODV

Now Comes to: Introduction Framework of TAODV Trust model for TAODV Routing Operations in TAODV Analyses and Simulations Conclusion

Representation of Trust Use Opinion to represent trust: A two-dimensional, but three-element 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 We define that

Combination of Trust Discounting Combination: Combine trusts along one path Combine Equation: Let

Combination of Trust (con’d) Consensus Combination: Combine trusts from several paths Combine Equation: Let

Mapping Between Evidence and Opinion space Mapping from evidence space to opinion space: α is a parameter imply the change rate of b, d, and u we can adjust it to meet our application p : positive evidences n : negative evidences

Mapping Between Evidence and Opinion space (con’d) Mapping from opinion space to evidence space: We can update trust information from evidence space mapping to opinion space, or vice versa

Now Comes to Introduction Framework of TAODV Trust model for TAODV Routing Operations in TAODV Analyses and Simulations Conclusion

Trust Recommendation Exchange trust information Three types of message: TREQ: Trust REQuest TREP: Trust REPly TWARN: Trust WARNing Broadcast TWARN when a node’s disbelief value is zero

Trust Recommendation (con’d) Message Structure TREQ  TREP 

Trust Judgement Predefined trust judging rules b d u Actions > h Request and verify digital signature Distrust a node till next certificate renewal Trust a node and continue routing ≤ h b – belief d – disbelief u – uncertainty h – threshold which can be adjusted to meet different security level (default h=0.5)

Trust Update Update of Evidences Update of opinion Successful Communication Positive events: p++ Failed Communication Negative events: n++ Mapping from opinion space Update of opinion Combination from different recommendations Mapping from evidence space

Routing Table Extension Add three fields into original routing table Positive events Negative events Opinion New routing table format DestIP DestSeq ... HopCount Lifetime Positive Events Negative Opinion

Routing Message Extension Add such fields into original routing messages Trust information, or Digital signature information RREQ  TRREQ RREP  TRREP Message structure: original routing information … trust information or signature information

General Process of TAODV On initialization, each node’s opinion towards others is (0,0,1), which means total uncertainty of other nodes’ trustworthiness. Nodes perform signature authentication during the initialization period. After some trust exchanges and data communications, thus with the increase of either positive or negative events, the uncertainty will be decreased and the trust relationship among nodes are forming. When the trust relationship in the network has been established, the authentication of nodes will mainly use trust authentication.

Trusted Routing Discovery P D S C N S originated a routing request to D C is the current node P is C’s precursor, N is the next hop Suppose threshold=0.5

Routing Process at Current Node Trust exchange step1: Authenticate P step2: Authenticate S step3: step4: Authenticate D

Routing Process at Current Node U>0.5 or b,d,u<=0.5 Wait for RREQ Trust exchange for opinions to S, D, P Combine  opinion(C,P) Combine  opinion(C,S) Judge opinion(C,S) Have route? Signature authentication Judge opinion(C,P) Y N b>0.5 d>0.5 TRREP enqueue Correct? Deny Re-TRREQ Combine  opinion(C, D) Judge opinion(C, D)

Now Comes to: Introduction Framework of TAODV Trust model for TAODV Routing operations in TAODV Analyses and simulations Conclusion

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.

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.

Simulation Environment Simulator: ns-2 Number of Nodes 30 Source-Destination Pairs 12 Simulation Fields 670*670m Simulation Time 360s Node Velocity Range 0-10m/s Source Packet Rate 4pkts/s Source Data Packet Size 512 bytes Physical Link Bandwidth 2Mbps Nominal Radio Range 250m

Selected Simulation Results Throughput of receiving bits VS Average End2End delay (pause time: 10s)

Conclusion TAODV is a trusted routing protocol which cooperates with a self-organized key management mechanism. It introduces less computation overheads than previous secure routing protocol solutions and also guarantee a certain security level. It performs trusted routing in a self-organized way.

Q&A Thank You!