wireless network keys management what is wsn ? steven du id: 3880740. csi 5148

Wireless Network Keys Management

What is WSN ?

Steven Du ID: 3880740. CSI 5148

Wireless Network Keys Management

Communication Security between sensor node

Because of memory and computation constraint in WSN

use symmetric keys for encryption and decryption sensors use common shared key to encrypt and

decrypt common shared keys are pre-distributed or

computed by specific scheme

The Globus Toolkit 4 Programmer's Tutorial Borja Sotomayor, University of Chicago, Department of Computer Science. Copyright © 2004, 2005 Borja Sotomayor

Wireless Network Keys Management

Key establishment schemes

Definition of key establishment:The algorithm or method for sensors to setup (or exchange) their common shared key for communication data

Main requirements on key establishment schemes:1. Availability : The network service is available without limitation with key

establishment 2. Authenticity: Ability for verifying that the message sent by a node is

authentic.3. Confidentiality : The key establishment technique should protect the

disclosure of data to unauthorized parties.4. Integrity : No falsification of data during transmission.

Key Pre-distribution in Wireless Sensor Networks when Sensors are within Communication Range Sushmita Ruj, Amiya Nayak and Ivan Stojmenovic

Wireless Network Keys Management

WSN symmetric key establishment steps:1. Key pre-distribution: Preload keys into each sensor nodes before WSN

deployment. 2. Shared-key discovery: Setup connection between two sensor nodes in their

communication range by finding common shared key.3. Path-key establishment : establishment of communication path and path key

between two unconnected sensor nodes. Path: linked nodes chain between two nodes without direct connectionPath key: Common shared key used by the linked nodes in path to transfer message

B

S

E

C

F

D

K

G

Key sb

Key be

Key bcKey SD

Key ef

Key fg

Key

gd

Key kd

Key

fk

Wireless Network Keys Management

WSN symmetric key establishment steps:1. Key pre-distribution: Preload keys into each sensor nodes before WSN

deployment.

B

S

E

C

F

D

K

G

{2, 3, 4, 5, 9}

{5, 7, 4, 9 1}

{3, 8, 1, 0 7}

{6 ,2, 8, 9 0}

{3 7, 9, 2, 4}

{5, 7, 4, 9 1}

{9, 2, 6, 3 1}

{1, 6, 4, 7 8}

Share key ?

Wireless Network Keys Management

WSN symmetric key establishment steps:2. Shared-key discovery: Setup connection between two sensor nodes in their

communication range by finding common shared key.

B

S

E

C

F

D

K

G

{2, 3, 4, 5, 9}

{5, 7, 4, 9 1}

{3, 8, 1, 0 7}

{6 ,2, 8, 9 0}

{3 7, 9, 2, 4}

{5, 7, 4, 8, 4}

{9, 2, 6, 3 1}

{1, 6, 4, 7 8}

Share key ?

Share

key ?

Shar

e ke

y ?Share

key ?

Share

key ?

Share

key ?

no !

Wireless Network Keys Management

WSN symmetric key establishment steps:

B

S

E

C

F

D

K

G

{2, 3, 4, 5, 9}

{5, 7, 4, 9 1}

{3, 8, 1, 0 7}

{6 ,2, 8, 9 0}

{3 7, 9, 2, 4}

{5, 7, 4, 8, 4}

{9, 2, 6, 3 1}

{1, 6, 4, 7 8}

Yes, 4,9

Yes 8

Yes 4,7

2. Shared-key discovery: Setup connection between two sensor nodes in their communication range by finding common shared key.

Yes 1,7

Wireless Network Keys Management

WSN symmetric key establishment steps:3. Path-key establishment : establishment of communication path and path

key between two unconnected sensor nodes.

B

S

E

C

F

D

K

G

{2, 3, 4, 5, 9}

{5, 7, 4, 9 1}

{3, 8, 1, 0 7}

{6 ,2, 8, 9 0}

{3 7, 9, 2, 4}

{5, 7, 4, 8, 4}

{9, 2, 6, 3 1}

{1, 6, 4, 7 8}

4, 5, 9

8

4, 7

1,7

Wireless Network Keys Management

WSN symmetric key establishment steps:

B

S

E

C

F

D

K

G

Key sb

Key be

Key bcKey SD

Key ef

Key fg

Key

gd

Key kd

Key

fk

3. Path-key establishment : establishment of communication path and path key between two unconnected sensor nodes.

Wireless Network Keys Management

WSN symmetric key establishment steps:1. Symmetric key establishment with Polynomial in finite field.

B

S

E

C

F

D

K

G

Id =7

I8 = 9

Id = 9 Id = 15

Id = 3

Id = 9

Id = 11

Id = 13

Wireless Network Keys Management

WSN symmetric key establishment steps:1. Symmetric key establishment with Polynomial in finite field.

B

S

E

C

F

D

K

G

Id =7

I8 = 9

Id = 9 Id = 15

Id = 3

Id = 9

Id = 11

Id = 13

What is

common ke

y ?

What is

common ke

y ?

Wireless Network Keys Management

WSN symmetric key establishment steps:

B

S

E

C

F

D

K

G

Id =7

I8 = 9

Id = 9 Id = 15

Id = 3

Id = 9

Id = 11

Id = 13

What is

common ke

y ?

22 3 yyxx

What is

common ke

y ?

1. Symmetric key establishment with Polynomial in finite field.

Wireless Network Keys Management

WSN symmetric key establishment steps:

B

S

E

C

F

D

K

G

Id =7

I8 = 9

Id = 9 Id = 15

Id = 3

Id = 9

Id = 11

Id = 13

What is

common ke

y ?

22 3 yxyx 22 3 yyxx

What is

common ke

y ?

4921737 222 yyyy

8127939 222 yyyy

1. Symmetric key establishment with Polynomial in finite field.

Wireless Network Keys Management

WSN symmetric key establishment steps:

22 3 yxyx 8127939 222 yyyy 8127939 222 yyyy1. Symmetric key establishment with Polynomial in finite field.

Each node can make security communication with other nodes in its communication range

Wireless Network Keys Management

Triple Key DistributionWhat is triple key distribution?

a common key discovery scheme among 3 sensor nodes

Y

X

Z

Common triple shared key

Y

X

Z

Common triple shared key

Wireless Network Keys Management

Triple Key Distribution

Why triple key distribution? path key establishment verifying the relayed message in path is authentic detect fault/malicious nodes

K{s, c, b}

BS C DKKey SC Key BKKey CB Key KD

secK secK secK secK

K{c, b, k}

K{b, k, d}

Wireless Network Keys Management

Triple Key Distribution

How triple key is distributed? any three full connected nodes share an unique common key any three string connected nodes share an unique common key

Two schemes:A.full connected triple keys distribution

B.String connected triple keys distribution

Wireless Network Keys Management

Triple Key Distribution (full connected triple nodes)

Triple nodes that share an unique triple key: BCS, BCE, ECK, EFK, FGK, DGK

Y

X

Z

Common triple shared key

B

S

E

C

F

D

K

G

Key sb

Key be

Key bcKey SD

Key ef

Key fg

Key

gd

Key kd

Key

fk

Key b

e

Key EK

Key KG

Key CS

Wireless Network Keys Management

Triple Key Application (full connected triple nodes)

K{s, e, c}

BS

E

C

F

DK

G

Key SC

Key

SE

Key CG

Key B

G

Key BKKey CB Key KD

Key

bc

Key

GK

Key EB

Key FD

Key E

C

Key F

K

secK secK secK secK

K{c, e, b}

K{b, f, k}

K{k, f, d}

K{c, b, g}

K{b, k, g}

C compare the message relayed by B to the sent message.Are they same? Yes? Done!No? Node B is in trouble, report!

Wireless Network Keys Management

Triple Key Distribution (String connected triple nodes)

B

S

E

C

F

D

K

G

Key sb

Key be

Key bcKey SD

Key ef

Key fg

Key

gd

Key kd

Key

fk

Key b

e

Triple nodes that share an unique triple key:SBE BCK CEF EFK FGD KDG EFGSBC BEF CKF ECK FKD CKD KFG

Y

X

Z

Common triple shared key

Wireless Network Keys Management

Triple Key Application (String connected triple nodes)

K{s, c, b}

BS C DKKey SC Key BKKey CB Key KD

secK secK secK secK

K{c, b, k}

K{b, k, d}

Wireless Network Keys Management

Triple Key Application (String connected triple nodes)

K{s, c, b}

BS C DKKey SC Key BKKey CB Key KD

secK secK secK secK

K{c, b, k}

K{b, k, d}

C: does node B correctly transfer my message to node K?

C compare the message relayed by B to the sent message.Are they same? Yes? Done!No? Node B is in trouble, report!

Wireless Network Keys Management

Analysis of triple key scheme

Security analysis:a compromised intermediate node possibly refuses or relay fake data frame. Because of acknowledge mechanism, its behaviour is monitored, found and kicked out of the network.

S Y DKey {?, S, Y}

Key {S, Y, D}

Key {S, Y, D}

Does node Y relay my message?No node Y stopped work, broadcast to whole WSNYes compare the relayed message. is the relayed message same as I sent?No node Y is compromised, broadcast to kick off Y

Wireless Network Keys Management

Several possible triple key establishment algorithms

Symmetrical polynomial for triple key computation

x, y, z are the ID of each node in the triple nodes

139999997 222222333 zyzxxzxyyzyxxyzzyx

X=10, y=11, z=12 85186

Wireless Network Keys Management

Triple key management in WSN?

a) A wireless sensor network with n nodes

b) The possibility for any two nodes to setup direct link is p

c) Possible average number of triple keys in each node S

full connected triple nodes3*

3P

nS

String connected triple nodes)1(**3

2 PPn

S

Wireless Network Keys Management

Triple key in cluster based network

Wireless Network Keys Management

Triple key in cluster based network

WSN network nodes density = DDeployment area = SCommunication radius = rCluster based WSN

Number of cluster headers

)*/(* 2rSCH C is a constant number , describes the WSN nodes deployment overlap level >1 Average nodes number in one cluster

2** rDn

Suppose the possibility of link between any two nodes in same cluster is P, we have:

Wireless Network Keys Management

Triple key in cluster based networkstring connected triple nodes

Average number of triple keys for each node

)1(*2

1P

nT