## 6 Trusted Routing Operation in AODV
### Trusted Routing Discovery  
In this section, we have described a general procedure for trust route discovery with an example shown in Figure 6a, also the route path from the source \(S\) to the destination \(D\) is uncovered. \(S\) will broadcast an TREQ message to discover a route path to \(D\). Node \(V\) is an intermediate node along this path, and nodes \(V_{1}\) to \(V_{4}\) are its four neighbors. When \(V\) receives the re-broadcast TREQ message from \(V_{1}\), it will perform such operations as illustrated in Algorithm 1.  
Specifically, in the above algorithm, node V wants to verify node \(V_{1}\)'s trustworthiness. It then collects its neighbors recommendations towards \(V_{1}\), and combines these opinions together using the combination operation as described in Section 5. Node \(V\) originally has opinions about \(V_{1}\) as \(w_{V_{1}}^{V}\). The indirect opinions it receives from its neighbors are: \(w_{V_{1}}^{VV_{2}},w_{V_{1}}^{VV_{3}},w_{V_{1}}^{VV_{4}}\), where \(w_{V_{1}}^{VV_{2}}\), shows opinion of \(V\) on \(V_{1}\) as advised by node \(V_{2}\) and so on. We can illustrate the trust recommendation relationships using Figure 6b, where the arrows denote opinion directions. First, \(V_{1}\) calculates the following opinions using Discounting operation:  
\[\begin{split} w_{V_{1}}^{VV_{2}}&=\bigtriangleup(w_ {V_{2}}^{V},w_{V_{1}}^{V_{2}})\\ w_{V_{1}}^{VV_{3}}&=\bigtriangleup(w_{V_{3}}^{V},w_ {V_{1}}^{V_{3}})\\ w_{V_{1}}^{VV_{4}}&=\bigtriangleup(w_{V_{4}}^{V},w_ {V_{1}}^{V_{4}})\end{split} \tag{15}\]  
Figure 5: Trust information exchange between interacting nodes using three kind of route information i.e., TREQ, TREP and TWARN are shown with yellow green and red colors.  
Figure 6: (**a**) General behavior of vehicles in performing trusted route discovery. (**b**) An example of trust recommendation from node \(V\) to node \(V_{1}\).  
Second the new opinion can be combined as \(w^{V}_{V_{1}}=w^{V(V_{2},V_{3},V_{4})}_{V_{1}}\), also by using Lemma 1  
\[\bigtriangleup(w^{V}_{V_{1}},\Theta(w^{V(V_{2},V_{3},V_{4})}_{V_{1}}))\equiv \Theta(\bigtriangleup(w^{V}_{V_{2}},w^{V_{2}}_{V_{1}}),\bigtriangleup(w^{V}_{ V_{3}},w^{V_{3}}_{V_{1}})),\ldots\ldots,\bigtriangleup(w^{V}_{V_{4}},w^{V_{4}}_{V_{1 }})\big) \tag{16}\]  
After that newly computed opinion is judged according to our rules given in Algorithm 1.  
Receive an \(TREQ(S,D)\) or an \(TREP(S,D)\) from V1;  
/*Verify the trustworthiness of \(V_{1}\)*/ Broadcast \(TREQ(V_{1})\) to request the opinions from \(V\)'s neighbors to \(V_{1}\); Receive opinions from \(V\)'s neighbors: \(\omega^{V_{2}}_{V_{1}},\omega^{V_{3}}_{V_{1}},\omega^{V_{4}}_{V_{1}}\)  
Combine these opinions together and get a latest: \(\omega^{V}_{V_{1}}\)  
Exchange opinions about \(V_{1}\) with its neighbors \(w^{V}_{V_{2},V_{3},V_{4}}\).  
/* \(\omega^{V}_{V_{1}}\
eq U\) and Judge the next step using conditions set in Table 1 */  
_if \(b^{V}_{V_{1}}\geq 0.5\)_  
trust \(V_{1}\) and forward RREQ/RREP  
_elseif \(d^{V}_{V_{1}}\geq 0.5\)_  
distrust \(V_{1}\) for expiry time  
_elseif \(u^{V}_{V_{1}}\geq 0.5\)_  
request and verify digital certificate  
_else_  
/* the confidence about trustworthiness is decreased*/  
request and verify \(V_{1}\) certificates, by default  
_endif_  
**Algorithm 1** Trusted Routing Discovery.