研 究 生：蔡憲邦指導教授：柯開維 博士

Design of Efficient and Secure Multiple Wireless Mesh Network

具安全性及自我組織能力的無線網狀網路

2005/7/15 2

Outline

Introduction Background Design a Secure WMN Security Analysis Conclusion

2005/7/15 3

Introduction (1/2)

Wireless Mesh Network Properties. Security Problem.

Wireless Security Problem Attacks. Secure solution.

2005/7/15 4

Introduction (2/2)

This thesis Tree topology Define the WMN’s basic functions Security issue Compare with other security issue

2005/7/15 5

Wireless Mesh Network (WMN)

Full & Partial mesh network. Omni directional & directional. Benefit:

Reduction of install cost Large-scale depolyment (last mile) Reliability Self-management

2005/7/15 6

WMN’s Architecture

Wireless Gateway

Access Point

Mobile

Wired Network

Wireless Gateway

AP

AP

Mobile

Mobile

Mobile

Mobile

2005/7/15 7

Wireless Security

Wireless Environment Open media Unlicensed ISM band

Wireless Attacks Infrastructure Ad hoc

2005/7/15 8

Wireless Attacks

Infrastructure Insertion Interception and Monitoring Jamming

Ad hoc Black hole Impersonation

2005/7/15 9

Wireless Security Solutions

Main Purposes Authentication Data encryption

Infrastructure WEP IEEE 802.1x

Ad hoc Share Key Public Key

Infrastructure (PKI)

2005/7/15 10

WEP

Wired Equivalent Privacy Integrity & Encryption Drawbacks:

Key size is too small (only 40 bits) Key Sequence Reuse (Initial Vector) Message can’t be Authenticated

2005/7/15 11

IEEE 802.1x (1/2)

Provide network access authentication.

Supplicant, Authenticator and Authentication Server.

Drawback: One-way authentication. Not protect authentication.

2005/7/15 12

IEEE 802.1x (2/2)Supplicant Authenticator Authentication Server

Authentication

Association

EAP req

EAP res

forward(unicast,Auth_message)

req_auth(unicast,auth_info)

req_auth(auth_info)

res_auth(auth_info)

res_success

session key exchange

EAPOL start

2005/7/15 13

Share Key

Use one key to authenticate and encryption in ad hoc network.

Drawbacks: Only one key Non-repudiation Key management

2005/7/15 14

Public Key Infrastructure

Key feature of public key cryptosystem Two keys: Public Key & Private Key Computational infeasible to

determine decryption key. Drawbacks

Certificate Authority (CA) Spend a lot of time to en/decrypt.

2005/7/15 15

Outline

Introduction Background Design a Secure WMN Security Analysis Conclusion

2005/7/15 16

The Properties of WMN

Similar to ad hoc network AP should select a routing path. The routing path is always fix.

Most data are sent to WG. My propose: Tree Topology.

2005/7/15 17

Tree Topology

A

B

C

D

E

F

G

H

I

J

A

B

C

D

E

F

G

H

I

J

(a) (b)

2005/7/15 18

WMN’s Relationship Supplicant Authentication Agent

Manage supplicants Help supplicant to

authenticate. Management System

Authentication server Maintain WMN

(b)

A

Authentication Agent

Supplicant

D

E

F

G

H

I

JManagement system(MS)

2005/7/15 19

Locally Secure Management

Different path, different secure channel.

AA only maintain his supplicants. Session key Authentication

a

b c

d e f g

h

(1) (2)

(3) (4) (5) (6)

(7)

d

(8)

d d

(9) (10)

2005/7/15 20

Two functions of WMN

Self-Organization When a new AP joins...

Self-Configuration Self-healing

When a AP occurs failure… Self-reconfiguration

When a AP not neighbor joins or fails…

2005/7/15 21

Self-OrganizationSupplicant Authentication Agent Management System

1.Req_Start(broadcast)

2.Resp_Start(unicast,infos)

3.Req_Join(unicast,join_message)

5.Req_Join_f(unicast,join_message)

6.Resp_join_f(unicast,auth_infos)

7.Req_Auth(unicast)

8.Resp_Auth(unicast,auth_info)

9.Resp_Success(nodie_id,Sign)

10.Session Key Exchange

4. Session Key Exchange

2005/7/15 22

Trust Model

Supplicant → WMN Group Key: Session key exchange first Confirm key: Authentication

WMN → Supplicant WMN’s Public Key Signature

2005/7/15 23

Choose Authentication Agent Two factors

Hop count Node loading

1. Choose the node has smallest hop count value.2. If there are two nodes has equal hop count value.

1. Compare their node loading value.2. Select the smaller one.

2005/7/15 24

Session Key Exchange

Session key exchange first. Session key should be modified

periodically. Default Key: groupK

2005/7/15 25

Send Key_Update to Authentication

Agent

Receive Key_Update &

Generate a new key

Finish

Supplicant Authentication Agent

Send new key encrypted by old key to Supplicant

Receive new key

Send Key_Updated

encrypted by new key

Receive Key_Updated

Is decrypted right?

Send Key_Update_ok

to Supplicant

yes

Is receive Key_Update_o

k?

yes

Restore old key

no

2005/7/15 26

Self-Configuration (1/2)

Self-Healing Determine the authentication agent

fail. Start Self-Organization process.

a

d

h i j

e f

b c a

d

h i j

e f

b ca

d

h i j

e f

b c a

d

h i j

e f

c

(a) (b) (c) (d)

2005/7/15 27

Self-configuration (2/2)

Self-reconfiguration

a

e

i j k

f g

b c

m n o

l

h

d

p

a

e

i j k

f g

b c

n o

l

h

d

p

a

e

i j k

f g

b c

n o

l

h

d

p

a

e

i j k

f g

b c

m n o

l

h

d

p

(a) (b) (c) (d)

2005/7/15 28

Outline

Introduction Background Design a Secure WMN Security Analysis Conclusion

2005/7/15 29

Security Issue

Message encryption: data & control

Locality security Trust model Session key exchange first Period session key exchange

2005/7/15 30

Attacks Defense

Man-in-middle (MIM) Forge AP Session Hijack Route Swindle Denial of Service (DoS)

2005/7/15 31

MIM & Forge AP

Man-in-Middle (MIM) Use session key create secure

channel. Period session key exchange.

Forge AP Period session key exchange.

2005/7/15 32

Session Hijack

Session key exchange first.Supplicant Authenticator Attacker

1.Authentication

2.Association

3.EAP req

4.EAP res

5.Req_auth(auth_info)

6.Resp_auth

7.Resp_success

8.Disassociation

9.Transmission

2005/7/15 33

Route Swindle

Use signature prove node’s legality.

a

c

b

f

e

d

h

g

a

c

b

f

e

d

h

g

(a) (b)

2005/7/15 34

Denial of Service

Attack: Limited CPU and memory. Continually send streams of

association and disassociation packets. Solutions:

There are not any solution to solve this problem.

Self-healing procedure

2005/7/15 35

WMN Security Comparisons

2005/7/15 36

Conclusion

Tree based secure architecture was proposed.

Define WMN’s basic functions of WMN.

Analysis WMN’s security problems. Compare with other security issue.

2005/7/15 37

Future Work

Consider more available attacks. Mobile mesh network. Other application:

Sensor network Ad hoc network

2005/7/15 38

The End, Thank You