Table 6 Trust metric

Multifaceted approach

Time closeness (T _c )

Location closeness (L _c )

Role-based trust value (T _r ) :

∙A u t h o r i t y∙E x p e r t∙S e n i o r i t y∙O r d i n a r y

Experience-based trust value (T _e ): depends on the number of interaction

TRIP

Direct previous experiences with the target node (Rep _ij )

Recommendations from other surrounding vehicles (Rec _kj )

Recommendation from central authority through roadside units (Rec_RSUj )

Data-centric

Dynamic trustworthiness factors, e.g., location and time (μ _l )

Event-specific trust (λ _j )

Security status (s(v _k ))

Type of vehicle ((v _k ))

RMCV

Content similarity (supprt(c))

- Maximum distance of content between two messages in the same cluster

- Possible maximum distance - number of messages

Content conflict (Con _c )

Route similarity (Path _c )

- Number of messages in the cluster

- Number of source providers

- Number of distinct vehicles in the routing paths of messages in the same cluster

Intrusion-aware trust model

Confidence value (C _i )

- Location closeness (L _c )

- Time closeness (T _c )

- Location verification (L _v )

- Time verification (T _v )

Total number of sender nodes (\(n_{x_{k}}\))

Reputation-based trust model

Real event frequency (E _f )

Standard frequency of event (E _s )

Degree behavior deviation (D _k )

Number of all vehicles sent the message to other vehicles (m,n,k,l)

ERS

Event reputation value: indicates the intensity degree of an event

Event confidence value: indicate the reliability extent of an event and the value is the number of vehicles that received the message

RATE

Observation factor (τ)

- Distance from vehicle to event

- Maximum detection range of the vehicle

- Number of sensors that can detect the event

- Total number of sensors equipped in the vehicle

feedback factor (η)

BTM

Beacon-based Trust (T _bea)

- Similarity between beacon and estimate value (Sim_cos)

Vehicle’s position

Velocity

Drive direction

Direct event-based trust ( T _devt )

- Similarity between historical beacon and received event message (Sim_tan)

Vehicle’s position

Velocity

Drive direction

- Distance between the message receiver and the message transmitter (Δ d)

- Time delay between the event message time-stamp and the receiver’s current time-stamp (Δ t)

- Maximum transmission distance (D _max)

- Maximum transmission delay (T _max)

Indirect event-based trust (T _evt)

Recommendation of other vehicles (T _opn)

Reputation and trust compositing (T _rep)

RaBTM

Opinion confidence of RSU (O _rsu)

Direct trust value (\(T_{\text {devt}}^{r,s}\))

- Transmission distance

- Transmission delay

Distance between sender and RSU (D _tot)

Distance between RSU and event (d _r,s )