Key Distribution and Route Selection in Wireless Sensor Networks

Key Distribution and Route Selection
in Wireless Sensor Networks

Nathan Lewis, Noria Foukia

{
ndlewis,nfoukia
}@
infoscience.otago.ac.nz

Information Science Institute

University of Otago

Dunedin, New Zealand

Objectives

•
Efficiency of distribution of pair
-
wise
encryption keys

•
Reliability of route selection


Overview

•
Key Distribution

–
Trust

–
Neighbor
-
based key distribution

•
Route Selection

–
Trust and Cost

–
Expenditure

•
Avoiding Loops

–
Testing routes

Key Distribution

•
By Base Station

–
All keys created by the Base Station

–
Nodes must communicate with the Base Station
to receive pair
-
wise keys

–
Nodes may be many hops from the Base Station

Key Distribution

•
By Neighbor

–
Common trusted neighbor can create a key

–
Initial trust calculation

–
Communications savings

Number of transmissions/node required for all nodes to
acquire pair
-
wise keys with their immediate neighbors.

40
50
60
70
80
90
100
100
200
300
400
500
Key Distribution by Neighbors - Degree = 10
Key Distribution by BS - Degree = 10
Key Distribution by Neighbors - Degree = 15
Key Distribution by BS - Degree = 15
Route Selection

•
Trust and Cost

–
Route Trust
(TR) is the minimum of the trust
values that each node has for the next hop on the
route

–
Route Cost
(CR) is the sum of the costs of each
hop to the destination

–
TR
A→B →BS

= min(TN
A →B
, TR
B →BS
)


CR
A →B →BS

= CN
A →B

+ CR
B →BS

Route Selection

•
Expenditure

–
How much we expect to pay to use a given route

–
E
A

= CR
A

+ (1
–

TR
A
)CR
B

•
CR
A

is the cost to use route A

•
(1
–

TR
A
) is the probability of route A failing

•
CR
B

is the cost to use route B

–
E
B

= CR
B

+ (1
–

TR
B
)CR
A

•
Compare two routes

–
Calculate E
A

and E
B

and select route with smaller
Expenditure

•
Multiple routes (C, D, ...)

Avoiding Loops

•
Loss of route information messages

–
Inconsistent picture of the state of the neighborhood

–
Possibility of selecting route that causes a loop

•
First send route test message

–
If message is received at destination then route does
not contain loop

–
If message returns to sender then sender knows a
loop exists and can avoid using that route

Summary

•
Neighbor
-
based pair
-
wise key distribution
reduces communications with large numbers
of nodes

•
Route selection requires only local
information, has simple calculation and only
requires a single pass through the list of
available routes

•
Reliable method of avoiding loops

Future work

•
May not need to test whole route, limit
number of hops

•
Add a reputation mechanism

•
Test in environment where nodes are mobile

•
Test in hostile environment with hostile nodes

•


nfoukia@infoscience.otago.ac.nz