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
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