1. TAODV: A Trusted AODV Routing Protocol for MANET
Li Xiaoqi, GiGi
Term Presentation

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

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

4. 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

5. 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

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

7. 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

8. 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

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

10. 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

11. 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

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

13. Framework of TAODV

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

15. 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

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

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

18. 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

19. 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

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

21. 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

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

23. 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)

24. 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

25. 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

26. 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

27. 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.

28. Trusted Routing DiscoveryP 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

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

30. 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)

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

32. 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.

33. 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.

34. 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

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

36. 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.

37. Q&A
Thank You!