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Calculating trust in sensor networks

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Figure 11: A graph of average reputations <strong>in</strong> a grid of nodes. The grid conta<strong>in</strong>s 17 normal<br />

nodes and 3 black hole -nodes.<br />

47.<br />

This way each scenario would produce 6 different results that could be used to assess how<br />

a <strong>trust</strong>ed rout<strong>in</strong>g protocol and a cha<strong>in</strong> of <strong>trust</strong> -scheme will operate <strong>in</strong> a <strong>sensor</strong> network.<br />

S<strong>in</strong>ce a <strong>trust</strong>ed rout<strong>in</strong>g protocol requires <strong>in</strong>formation about its neighbours before it will<br />

operate normally, the network was primed by transmitt<strong>in</strong>g random data between the<br />

nodes. This was implemented by two nodes on the opposite corners of the grid each<br />

download<strong>in</strong>g roughly 2 kB of data from each non-malicious node. In a 5x5 grid of nodes<br />

with 23 transmitt<strong>in</strong>g nodes and a 256 byte payload this would amount to around 170<br />

packets transmitted. At that po<strong>in</strong>t, every node will have a pretty good op<strong>in</strong>ion about its<br />

neighbours.<br />

5.1 Scenario 1: A cloud of nodes<br />

Scenario number 1 consists of 25 nodes aligned <strong>in</strong> a 5x5 grid. When malicious nodes are<br />

added to the grid, they are spaced as a cluster of 7 nodes near one side of the grid. Nodes<br />

<strong>in</strong> the opposite left lower- and right upper-corners function as the service ask<strong>in</strong>g nodes.<br />

46

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