Calculating trust in sensor networks

uilt between two or several nodes that agree to share the monitoring work for their area.
EEMP does not define strict timeslots for each node to do the monitoring. The individual
monitoring timeslots for each node are instead determined randomly and independently.
EEMP works by dividing each timeslot into two parts, the ON- and OFF-parts. Each
node then decides probabilities that it will start monitoring during the ON-slot, and a
probability that it will stop monitoring during the OFF-slot. Shared monitoring is random,
with the off chance that at some point, no node is monitoring the area.
The rating component draws information from the monitoring component and gathers
indirect observations from other nodes. First hand observations define the trust of a node
by a number between 0 and 1. Trust is calculated as:
riski = frequencyi
frequencymax
Where frequencymax is the maximum amount of bad behaviour that is tolerated per time
and frequencyi is defined as:
frequencyi = badbehaviouri
timei
Where badbehaviouri is the amount of bad behaviour noticed about node i and timei is
the amount of time spent monitoring node i.
The scheme then works by assigning untrustworthy nodes a high number, indicating high
risk. Trustworthy nodes receive a low number, indicating low risk.
Nodes may notify other nodes about node i by transmitting their risk for node i. These
indirect observations are added to the overall risk by.
riski = W ∗ riskdirect,i + (1 − W ) ∗ riskindirect,i
Where W is a weighing factor that is used to define how much emphasis direct observa-
tions are given over indirect observations. What is notable here is that WSNodeRater
automatically trusts indirect observations and does not consider or weight the source of
the information.
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