VANET Thread Based Message Trust Model Abdul Rehman, Asad Ali, Riaz ul Amin, Attique Shah

Faculty of Information and Communication Technology, Balochistan University of Information Technology Engineering and Management Sciences, BUITEMS

Quetta, Pakistan Email: {abdul.rehman1, asad.ali, riaz.ulamin, attique.shah}@buitms.edu.pk

Abstract- Vehicular Ad-hoc Network (VANET) is an emerging

technology which enables us to communicate with other vehicles

on the go without any infrastructure. The lack of infrastructure

imposes some serious challenges over researchers for instance;

communication between the peers must be secure and protected

against any false information. During communication between

the vehicles the trust worthiness amongst vehicles is a very

critical issue. The problem with VANETs is that they lack

standards for trustworthiness of messages received from

different vehicles. Before acting on any received message, it must

be evaluated for truthfulness, as reacting on any malicious

message could lead the driver to misguidance and can cause

serious accidents. In this paper, we proposed a thread based trust

model that will evaluate the trustworthiness of the message on

the go. The model is based on creating multiple threads of single

situation.

I.INTRODUCTION

Since last decade wireless technologies have developed new dimensions in almost every area of communication.Communicating wirelessly between various vehicles on run time without the need of any infrastructure is one of the most demanding areas of mobile wireless communication that has many issues to be resolved yet. Vehicular Ad-hoc Network (VANET) is very effective for situations emerging on the road to avoid serious accidents and traffic congestion. Large metropolitan cities are in real search of traffic management especially in rush hours where VANET could prove to be the best solution, if used effectively. However, the problem with the VANET generated messages is that of the trustworthiness.The trust between the vehicles is very hard to establish due to limited time and very rare chances of interaction between same vehicles time and again [1]. Many models have been proposed for message trust with different techniques most of which use prior trust establishment [2]. Some models are so sophisticated and not suitable for real time situation. Still there is a need for a comprehensive framework for VANET based trust establishment. Due to high mobility and lack of interaction, the primary requirement is on spot message evaluation rather than establishing the trust which is secondary. Our model is purely based on evaluating the message rather than establishing the trust which have very low

chances to be used due to infrequent interaction between vehicles. Our model is based on multiple reports of a single situation which further creates threads while communication. Our work is based on real time trust level, where multiple reports of the event can increase the level of trust. In this paper we have presented a trust model for evaluating the truthfulness of reported event.

Rest of the paper is organized as follows. Section II consists of related work done in this area, section III contains our proposed model, and then we discuss conclusion and future work in section IV.

II.RELATED WORK

A lot of work has been done on trust models in VANET. [2]has carried out a detailed survey on VANET trust models and has evaluated different challenges of VANET & identifies different existing models for trust in VANET. The authors have also compared different models on the basis of their characteristics and have concluded that Managing trust for VANET is demanding issue. For the sake of simplicity, here we have categorized them into three types namely; entity based, data centric and hybrid approaches.

i) Entity-based: many entity based model have been proposed that are based on trust establishment between the vehicles for instance [3] presented architecture for secure vehicular communication. The framework they proposed is based on confidence tagging. They also categorize trust but were unable to formalize them to establish aggregated trust. In [4] the author has proposed a model that evaluates message on the basis of repute of the sender vehicle. Their model also features request based inquiry which increases time and may create problem in time critical situation. [5], they present a trust model in which vehicles are grouped off-line with some reputation. [6], they propose a fuzzy method to accept a critical message or not on the basis of trustworthiness of the sender. The entity based models are one of the earlier models developed which manage trust between vehicles, however, are not suitable for the ad hoc networks because there are rare chances of interaction between vehicles time and again ii) Data-centric: Data evaluation approach is based on examining the trust worthiness of data not the entities. [7]Proposed a framework for ephemeral ad hoc networks which is based on data reported from different nodes. The model

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calculates the probability of the event by evaluating the data using Dempster-Shafer Theory and Bayesian inference. This model uses too many variables and also depending on probability in life critical situations would not be appropriate. With this model calculation in high speed environment is very difficult like that in highways. [8] Proposed an algorithm for detecting malicious vehicles that passes false information in networks. The authors have proposed the certified administrative authorities to fine such malicious vehicles. [9] Proposed a model to sort out fake messages by observation of behavior of the reporter. Data oriented models are mostly based on the prior likelihood of the trustworthiness of message and takes a lot of time for calculation which is not suitable in fast movement of the vehicles and these models also do not provide any mechanism for establishing trust between the nodes. iii) Hybrid models: These models incorporate the features of the above two models. In [4], the authors have proposed piggybacking where each node gives its own opinion about the event which again involves different trust metrics. The model is not a sufficiently detailed one, as one opinion could affect other’s opinion and no procedures have been given to

overcome this issue. [10] has proposed solution based on validity of data. They assume that there are some trusted entities in the system. By evaluating number of reports, the model will infer the trust worthiness of the event. The major problem in this approach is that it always needs trusted vehicles, which is inappropriate in case of VANET. Zang and et al’s framework [11] evaluates message trust on the basis of collaborative feedback between peers about any particular event. Their approach also evaluates vehicular trust by behavior. In [1] the authors have proposed a model which estimates trust on the basis of vehicle’s behavior using Markova chain. Any vehicle in the model could update the trust matric of the neighbor according to its behavior. They have also sorted the selfish & malicious vehicles. The combined models are less elaborated to be applied in real time scenario and most of models have constant entities required for calculation which is not feasible in ad hoc networks especially VANETS. All the previous models show that there is need for a simple and comprehensive model to be applied in ephemeral and ad hoc network.

III.PROPOSED MODEL

Our proposed model is based on threads which can be virtually created by message propagation. The vehicles which report the situation are Reporter vehicles (Rv) and those who receive the message, are called Carrier vehicle (Cv). The trust level is denoted by (Tl). A unique identification will also be

assigned to reporting vehicle and event respectively (Rv_ID) and (E_ID). All the information regarding events will be stored locally in a database (DB).

Fig. 1 show a scenario where three different Rvs have reported an event E1. This increases the trust level as multiple Rvs have generated the event. If a Cv receives a message or a

thread message from the same Rv, it will not add to Tl of message. The trust level will be increased if and only if the message is received by different Rvs.

Fig. 1: Different Message Threads of Single Event

For any moment, the Tl on any particular Cv will be Tl =n-1,

where n is the number of Rvs. For example if an event generated from three Rvs, the Tl on the vehicle will be 2.

The proposed scheme is summarized in the algorithm below.

___________________________

Algorithm 1

_________________________________________________

1. Initialize

2. Tl =0

3. Event message received 4. check EID

5. if (EID is old) then 6. check Rv ID 7. if (Rv ID is new) then 8. modify, Tl=Tl+1 9. broadcast message with new Tl 10. update local DB 11. perform action accordingly

12. else

13. if (Rv ID is old) then 14. discard message

15. else 16. if (EID is old) then 17. broadcast message with Tl 18. update local DB 19. perform action accordingly

_______________________________________________

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Fig. 2: Flowchart of the Model Algorithm

IV.CONCLUSION

A very effective model for VANET message trust is proposed, that will increase trustworthiness of VANET messages, the model is very distinctive in its method and usable in real time emergency situation, it has also another uniqueness that the trust establishes only for a particular event and for next situation it again evaluates the message worth to be acted upon. In future, we plan to enhance the model that will establish apriori trust between the vehicles on the basis of behavior of the vehicles in a particular situation, for increasing the trustworthiness of the vehicles, so that it could be used for better evaluation of the message.

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