dept. of computer science & engineering, cuhk1 trust- and clustering-based authentication...

Dept. of Computer Science & Engineering, CUHK 1

Trust- and Clustering-Based Authentication Services in Mobile Ad Hoc Networks

Edith Ngai and Michael R. LyuProceedings 2nd International Workshop on Mobile Distributed Computing (MDC'04), Tokyo , Japan , March 23-26 2004


Outline

Introduction Related Work Models Security Operations Simulation Results Conclusion


Mobile Ad Hoc Networks

Infrastructure-less Multi-hops Wireless communications Highly mobile Dynamic topology Vulnerable to security attacks


Introduction

Certificate-based approach Fully distributed manner Detect false public key certificates Isolate dishonest users Propose a secure, scalable and distributed

authentication service Assure correctness of public key

certification


Related Work

Traditional network authentication solutions rely on physically present, trust third-party servers, or called certificate authorities (CAs).

Partially-distributed certificate authority makes use of a (k,n) threshold scheme to distribute the services of the certificate authority to a set of specialized server nodes.

Fully-distributed certificate authority extends the idea of the partially-distributed approach by distributing the certificate services to every node.


Related Work (Cont.)

Pretty Good Privacy (PGP) is proposed by following a web-of-trust authentication model. PGP uses digital signatures as its form of introduction. When any user signs for another user's key, he or she becomes an introducer of that key. As this process goes on, a web of trust is established.

Self-issued certificates issue certificates by users themselves without the involvement of any certificate authority.


Our Work

Propose a secure public key authentication service in mobile ad hoc networks with malicious nodes

An originally trust-worthy node may become malicious all of a sudden due to the invasion of hackers

Prevent nodes from obtaining false public keys of the others

Based on a network model and a trust model Security operations include public key certification

and trust value update


Architecture

Network Model Clustering-based network model for

obtaining a hierarchical organization of the network

Trust Model Trust model with an authentication metric

to maintain the trust values of different nodes

Security operations To detect and isolate malicious nodes


The Network Model

Obtain a hierarchical organization Minimize the amount of storage for

communication information Optimize the use of network bandwidth Direct monitoring capability is limited to

neighboring nodes Allow the monitoring work to proceed more

naturally Improve network security


The Network Model (Cont.)

Obtaining a hierarchical organization of a network is a well-known and well-studied problem

Related Clustering Techniques Weight-based clustering algorithms Max-Min D-cluster formation Weakly-connected dominating set Adaptive maintenance Zonal algorithm Location-aware clustering


The Network Model (Cont.)

Group 1

Group 2

Group 3

Group 4

The network is divided into different regions

Each region with similar number of nodes

Each of the group has a unique group ID


The Trust Model

Define a fully-distributed trust management algorithm that is based on the web-of-trust model, in which any user can act as a certifying authority

Use digital signatures as the form of introduction. Any node signs another's public key with its own private key to establish a web of trust

There is no need for any trust root certificates

Rely only on direct trust and groups of introducers in certification


The Trust Model (Cont.)

Authentication in ad hoc network without centralized authorities generally depends on a path of trust intermediates.

To evaluate the trusts from the recommendation of other reliable entities, the relying node should be able to estimate the trustworthiness of these entities

Many metrics have been proposed to evaluate the confidence afforded by different paths

Related approaches include metrics for directed graph, PGP’s three levels of trust, and path independence


The Trust Model (Cont.)

Define the authentication metric as a continuous value between 0.0 and 1.0

A direct trust is the trust relationship between two nodes in the same group

A recommendation trust is the trust relationship between nodes in different groups

Apply some equations to calculate and combine the trust values of the trust relationships on different paths

Update the trust tables accordingly


Assumptions

There is an underlying clustering algorithm in the network

Nodes are divided into groups with unique IDs Each node keeps exchanging information

about which groups the other nodes belong to Each node is able to monitor the behavior of

its group members and obtain their public keys

Each node keeps a trust table for storing trust values of other nodes


Security Operations

Public key certification It allows a node to obtain the public key

of another node securely A node sends request messages to

certain number of introducers for the public key certificates of the target node

Trust value update It updates the trust value of a node

based the trust values and relationships built up with other nodes in the network


Authentication in our network relies on the public key certificates signed by some trustable nodes, called introducers i1, i2, …, in

A trust path is formed by a recommendation trust relationship and a direct trust relationship

Public Key Certification

Whole Network

Group A Group B Group C Group D

s t ini1 i2

… … …

…

…

Direct trust

Recommendationtrust

…

...


Operations of Node

Select introducers Send request

messages to introducers

Collect and decrypt the messages

Compare the certificates, isolate dishonest nodes

Calculate trust value of the new node


Trust Value Update

Direct trust relationship means to believe an entity in its capability with respect to the given trust class

Recommendation trust expresses the belief in the capability of an entity to decide whether another entity is reliable in the given trust class and in its honesty when recommending third entities

s denotes the requesting node t denotes the target node Nodes i1, i2, …, in are the introducers Each Vs, i* and Vi*, t form a pair to make up a single

trust path from s to ti1

in

i2

…

s t

Vs,i1

Vs,i2

Vs,in

Vi1,t

Vi2,t

Vin,t


Trust Value Update (Cont.)

Compute the new trust relationship from s to t of a single path

Combine trust values of different paths to give the ultimate trust value of t

Insert trust value Vcom to the trust table of s

1221 )1(1 VVVV

,

1 1

1 (1 )i

i

m n

ncom i j

i j

V V

i1

in

i2

…

s t

Vs,i1

Vs,i2

Vs,in

Vi1,t

Vi2,t

Vin,t


Simulation Set-Up

Network simulator Glomosim

Evaluate the effectiveness in providing secure public key authentication in the presence of malicious nodes

Simulation Parameters

Network # of nodes 40

# of groups 4

% of trustable nodes at initialisation p

% of malicious nodes m

Public key request

Max # of introducers for each request 3

Min # of reply for each request 1

Simulation Time 10000s

# of query cycles 20

# of requests per cycle 40


Metrics

Successful rate % of public key requests that lead to a correct

conclusion Failure rate

% of public key requests that lead to an incorrect conclusion

Unreachable rate % of public key requests that cannot be made

due to not enough number of introducers


Ratings to % of Malicious Nodes

Ratings to % of Malicious Nodes

0

1020

3040

50

6070

8090

100

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% of Malicious Nodes

Ratin

g (%

)

Successful rate

Failure rate

Unreachable rate


Comparison on Successful Rate

Successful Rate to % of Malicious Nodes

0

1020

3040

50

6070

8090

100

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Succ

essf

ul R

ate

(%)


Comparison on Failure Rate

Failure Rate to % of Malicious Nodes

0

10

20

30

40

50

60

70

80

90

100

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Failu

re R

ate (%

)


Conclusions

We developed a trust- and clustering-based public key authentication mechanism

We defined a trust model that allows nodes to monitor and rate each other with quantitative trust values

We defined the network model as clustering-based The proposed authentication protocol involved new

security operations on public key certification, update of trust table, discovery and isolation on malicious nodes

We conducted security evaluation We compared with the PGP approach to

demonstrate the effectiveness of our scheme

dept. of computer science & engineering, cuhk1 trust- and clustering-based authentication...

Documents

computer science engineering

trust authentication

network security slide

web of trust

cuhk1 trust

trust value update slide

certificate services

users key