Trust Model Based Self-Organized Routing Protocol For Secure Ad Hoc Networks

1
Trust Model Based Self-Organized Routing
Protocol For Secure Ad Hoc Networks

• Li Xiaoqi
• CSE Department, CUHK
• 29/04/2003

2
Outline

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Conclusion
• Research Plan and Future Work

3
Now Come to

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Research Plan and Future Work
• Conclusion

4
What is Ad Hoc Network

• A kind of network without fixed infrastructure
  such as base stations or access points, which
  performs communications through wireless media
• Wireless applications in
• Military Operations
• Disaster Relief
• Meeting Room Setup for Conference
• Personal Area Networking

5
Characteristics of Ad Hoc Networks

• No fixed infrastructure
• Each node is a router
• Multi-hop routing by nodes cooperation
• Self-organization nature
• High mobility
• Prone to be attacked

6
Routing Protocols for Ad Hoc Networks

• AODV
• -Ad Hoc On-Demand Distance Vector Protocol
• DSR
• -The Dynamic Source Routing Protocol
• DSDV
• -Destination-Sequenced Distance Vector Protocol

7
Overview of AODV

• Discover routes when needed
• Mainly two types of routing messages
• RREQ Route Request
• RREP Route Reply
• Fixed-length messages
• Only one mutable field Hop Count

8
Route Discovery in AODV
RREQ
Broadcast
S
D
RREP
RREP
9
Now Come To

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Conclusion
• Research Plan and Future Work

10
Security Requirements in Ad Hoc Networks

• Confidentiality
• Authenticity
• Integrity
• Availability
• Non-repudiation
• Access Control

11
Attacks to Ad Hoc Networks
12
Common Solutions for Security

• Often assume
• A trusted authority to issue certificates.
• A centralized server to monitor the networks.
• A secret association between certain nodes.
• Disadvantages
• Destroy the self-organization nature of ad hoc
  networks.
• Limit the mobility of nodes.
• Single point of failure
• Less of efficiency and availability

13
Self-Organized Solutions for Security

• Properties
• Authenticate each other in a self-organized way
• Often issue certificate of a public key by nodes
  cooperation
• Often need node monitoring mechanism
• Disadvantages
• Need at least k neighbors to cooperate
• Monitoring mechanism is difficult to implement
  and is performance-consuming

14
Current Issues in Ad Hoc Networks

• Lack of security consideration
• Centralized server or trusted third parties
  destroy the self-organization nature
• Pure cryptographic solutions bring high overhead
• Current self-organized solutions lose flexibility

15
Our Solutions and Design Goals

• Design a suitable decentralized trust model that
  can be used for the security solutions of ad hoc
  networks.
• Apply this trust model to design a flexible
  self-organized key management scheme.
• Apply this trust model to design a secure and
  flexible self-organized routing protocol with
  lower overhead.
• Demonstrate the principle of the trust model and
  the security advantages of the resulting ad hoc
  networks.

16
Now Come To

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Research Plan and Future Work
• Conclusion

17
Trust Model for Ad Hoc Networks

• Overview of trust theory
• Trust is a basic aspect of human life.
• Trust is regarded as a measurable variable.
• Trust theory has been applied into the fields of
  E-Commerce
• Organization of nodes in ad hoc networks is
  similar as human society
• Apply trust theory to secure ad hoc networks

18
Previous Trust Models

• Direct and recommendation trust model
• Continuous value to represent trust
• Basis of many other trust models
• Recommendation protocol model
• Focus on the exchange of trust information
• Dempster-Shafer Theory based model
• Upper and lower bound pair to represent trust
• Trust matrix to represent trust relationship
• Combine two matrices using Dempster-Shafer theory

19
Previous Trust Models (Cond)

• Model using Fuzzy Logic
• Trust matrix to represent trust relationship
• Fuzzy logic to verify transactions
• Fuzzy logic to combine trust matrices
• Model using Subjective Logic
• Use Opinion to represent trust
• Opinion includes belief, disbelief, uncertainty
• Combine trust using subjective logic

20
Comparison of Trust Models

• Single trust value vs. Opinion
• Opinion with belief, disbelief and uncertainty
  can express more information
• Fuzzy logic vs. Subjective logic
• Fuzzy logic operates on certain measures about
  fuzzy propositions
• Subjective logic operates on uncertain measures
  about crisp propositions

21
Comparison of Trust Models (Cond)

• Shafer theory vs. Subjective logic
• Both introduce uncertainty
• No need to set upper or lower bounds of trust
  described in Shafer theory

22
Design Issues of Trust Model

• Definition of Trust
• Representation of Trust
• Combination of Trust
• Exchange of Trust Information

23
Our Trust Model

• Use Opinion to define and represent trust
• Combine trust opinions using subjective logic
• Define a trust recommendation protocol to
  exchange trust information

24
Definition and Representation of Trust

• Opinion a three-dimensional metric
• The opinion about the trustworthiness of x,
  denoted by ?x , is the triple defined by
• b(x) represent belief probability of believing
  x.
• d(x) represent disbelief probability of
  disbelieving x
• u(x) represent uncertainty probability of
  uncertainty about xs trustworthiness

25
Definition and Representation of Trust (Cond)

• Property of Opinion
• b, d, u is in 0,1
• bdu 1
• Opinion ?x (0.4,0.1,0.5) can be represented in
  the right figure.

26
Combination of Trust

• Discounting Combination
• Combine trusts along one path
• Combine
• Consensus Combination
• Combine trusts from several paths
• Combine

27
An Example of Combining Trust

• A want to know
• Bs trustworthiness

28
Trust Recommendation Protocol

• Exchange trust information
• Three types of message
• TREQ Trust Request
• TREP Trust Reply
• TWARN Trust Warning
• Message structure

29
Our Trust Model vs. Subjective Logic Trust Model

• Simplify the representation of trust, which is
  more suitable for ad hoc networks
• Propose a trust recommendation protocol to
  exchange trust information
• Handle the dynamic of trust which is not
  mentioned in subjective logic

30
Now Come To

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Research Plan and Future Work
• Conclusion

31
Assumption of Our Trusted Routing Protocol

• Ability to recover nodes neighbors.
• Reliability of broadcasting one-hop messages
• Uniqueness of nodes ID
• Capability of monitoring behaviors of one-hop
  neighbors
• Key management has been done before

32
Node Model

• One node has an opinion about others
• Each node maintains a trust table. For Example,
  As trust table is
• Initial opinion of a node in others eyes is
  (0,0,1)

33
General Framework
34
Cryptographic Technologies

• Use cryptographic schemes to do routing in the
  beginning of this network
• Adopt ideas in SAODV 42
• Digital signature authenticate the non-mutable
  fields of the messages
• Hash chains secure the only mutable field hop
  count

35
Overview of Trusted Self-Organized Routing
Protocol

• Effective when trust relationships have been
  established among most nodes
• Based on AODV routing protocol
• Criteria to determine whether a node can be
  trusted or not is
• belief0.5, disbelieflt0.5, uncertaintylt0.5
• Nodes cooperate to decide a opinion

36
Trusted Routing Discovery
37
Trust Update Algorithm

• Each value in a opinion is logically divided into
  5 levels. Every 0.25 is one level.
• Successful verification for ten times
• belief0.25, disbelief-0.125,
  uncertainty-0.125
• Failed verification for each time
• belief-0.125, disbelief0.25,
  uncertainty-0.125
• No verification during expiry time
• belief-0.375, disbelief0.125, uncertainty0.25

38
Trust Update Algorithm (Cond)

• If in opinion A to B,
• belieflt0 or disbeliefgt1
• Opinion(A?B) will be changed to (0,1,0)
• Node A broadcast this opinion using TWARN message
• Neighbors will re-calculate the opinion using
  trust combination algorithm
• B will be denied from As communication

39
Trusted Key Management

• Use trust model into key management
• Advantages
• Self-organization
• Flexible no limitation of at least k neighbors
• Lower overhead

40
Analysis

• Performance is increased
• No need to perform cryptographic calculations for
  every packet ? lower overhead
• Security is enhanced
• Combination of trust model, cryptographic schemes
  and monitor mechanism
• More reasonable and flexible
• Good nodes who become bad will be denied from
  network eventually
• Bad nodes who turn to good will be allowed
  accessing network again soon

41
Now Come To

• Introduction to Ad Hoc Networks
• Motivation and Design Goals
• Trust Model for Ad Hoc Networks
• Trusted Self-Organized Routing Protocol
• Conclusion
• Research Plan and Future Work

42
Conclusion

• A promising idea to apply trust model to secure
  ad hoc networks
• Node uses opinion to judge if another node is
  trustable
• Nodes cooperate to obtain a more accurate opinion
• Trusted routing protocol is
• Self-organized
• Lower-overhead
• More reasonable

• More secure
• More flexible

43
Research Plan and Future Work

• A better trust combination algorithm
• A better way to apply trust model into key
  management
• Study monitor or intrusion detection issues
• Improve trusted routing protocol to make it
  prevent or stand more attacks
• A detailed simulation evaluation using NS-2 or
  Glomosim simulators

44
QA

• Thank you !