Calculating trust in sensor networks

Another method of using the hop count of a route would be to count the multiplied
reputations of the route with the hop count:th root:
trustworthiness(x, y) = n
�
�
�
� n �
reputationi(i − 1)
One major benefit of this approach is that lower reputations will have a larger impact on
the total trustworthiness of the route.
To test the different metrics described above, we define three test scenarios and calculate
the trustworthiness with three of the four metrics, route average, hop count:th root and
square root. We will omit the aggregated-metric, as it is not easily compared to the other
three metrics. The most we can answer about the aggregated method is that the result
will lower with every hop, finally resulting in very low numbers.
Figure 8: Different methods of calculating chains of trust in a route consisting of good,
then bad, then good nodes.
Figure 8 shows the trust calculations of the three metrics when a packet traverses 11 nodes.
The reputations of the nodes decrease steadily from 0,9 to 0,1 as the packet moves from
hop to hop and then rise steadily back to 0,9. The average and hop:th root-methods each
react similarly to the reputations with the hot:th root-method returning more pessimistic
i=1
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