## 2 Related Work
### Securing VANET-Centralized Architecture Based on DoS Attacks and Other Related Attacks  
In a previous study [20], the authors proposed malicious node detection on vehicular ad-hoc networks. They used Dumpster Shafer theory to investigate DoS attacks. However, during the investigation it was discovered that it was not centered on secure storage solutions. In addition, hybrid multicast and unicast data transmissions were not used to investigate for real time detection of all forms of attacks, including HDSA attacks. Instead, the authors' investigation was centered on an artificial neural network-based technique, which used a self-organized map. In the investigation, the authors also used only a trace file to train the network, which works as an input to self-organize the map. This was in order to provide supervised learning to their network. Although, the authors used a self-organized map (SOM) classifier for detection of misbehavior nodes; the method used was not fully investigated or explained. Moreover, there were also limitations in investigation of the IEEE 802.11 standard data transmission technique. The IEEE 802.11 utilizes the DSRC technology to investigate communication of vehicles in the network. This is observed as a major limitation of the scheme. In a previous study [21], the authors proposed prevention of DoS attacks over a vehicular ad hoc network using a quick response table. However, based upon the proposed scheme, there was a limitation. This includes use of a clear security method that was required to secure the network. This requires urgent attention. Another limitation observed for the scheme was that the authors did not conduct an investigation regarding an efficient storage mechanism for the network deployment. In addition, there was no recommendation for any trustworthiness method, which would be used to secure the network. In addition, the detection of DoS attacks was only based upon certain forms of attacks, such as gray hole, Sybil, and black hole attacks only. However, these attacks are of different categories. Thus, the authors' investigation could not be considered appropriate, due to absence of investigation of DoS JSA, PD, and RCRCO overutilization, which relates mostly to the trustworthiness and efficient provision of data for RSU in VANET. However, it was discovered in the authors' investigation that the proposed security mechanism was merely a discussion method for routing in VANET. The routing method was only used to identify and eliminate the existing security threats. The authors did not recommend any real-time investigation of the methods used for investigation of trustworthiness in VANET. In a previous study [22], the authors proposed an efficient and lightweight intrusion detection mechanism for service-oriented vehicular networks (ELIDV). From the perspective of the authors, they designed and implemented ELIDV with the aim of protecting the network from only three kinds of attacks, namely DoS attacks, integrity targets, and false alert generation. In addition, the proposed ELIDV security method was also based upon a set of rules that detected malicious nodes promptly. However, the proposed method was not evaluated based upon high prediction accuracy evaluation of HDSA for VANET. Also, the authors' investigation concerning secure method provision in VANET was without consideration for any efficient storage mechanism. Therefore, it can be concluded that there was no trustworthiness protection provision in the network. In addition, another limitation that was discovered was that the DoS attack detection method used was not centered on any HDSA, including DoS JSA, PD, or RCRCO overutilization. The proposed scheme was also identified as having a limitation in designing a secure encryption and authentication mechanism. This would otherwise be used for providing a hybrid investigation of DoS attacks that would also include investigation of real-time data transmission in VANET.