## 2 Related Work and Motivations  
### Related Works  
Due to high mobility in VANETs, it brings the disconnection between nodes in urban scenarios. Therefore, we require a clustering protocol to achieve high stability as well as reducing control overhead. The author in [18] proposed a multi-hop broadcast protocol to efficiently disseminate emergency warning messages in a VANET with highway scenario. The authors in [19] proposed the lowest ID (LID) and highest degree (HD) algorithm. In the LID algorithm, the node with a lower identifier becomes a cluster head. In the HD algorithm, the node with the highest number of neighbors is selected as CH. The authors in [20] addressed the passive multi-hop clustering algorithm (PMC) to ensure the coverage and stability of the clusters. In [21], the authors studied the vehicle selection based on sigmoid function in which the vehicles with large object functions are selected as cluster heads. However, the proposed algorithm does not consider stability and connectivity between vehicles. Hence, to improve the network stability and connectivity, the network parameters that affect on the clustering and cluster head election is considered as the cost for clustering. Various routing protocols have been proposed secure routing to tackle the node's strong mobility. The author in [22] addressed an intelligent opportunistic routing algorithm for wireless sensor networks and applies it for e-healthcare. The author in [23] presented an intelligent trust sensing scheme with metaheuristic-based secure routing protocol for Internet of Things in [23], to identify the next hope by using a fitness function. However, it cannot avoid the attacker directly in order to select the next hope. The author in [24] proposed a blockchain-based secure routing protocol for opportunistic networks. In [24], only registered nodes can forward hello packets. If there is a new node, the node must be registered first, then it can forward the hello packet. Otherwise, the node cannot join the network. The author in [25] studied a trust-based secure intelligent opportunistic routing protocol to avoid the gray and black-hole attack in the wireless sensor networks. However, these works [22; 23; 24; 25] proposed secure routing that did not focus on sinkhole attack in VANET. The authors in [26] addressed the method of speed adaptive beacon broadcast (SABB) to propagate information in urban and highway environments. In [27], the authors exploited the vulnerability attacks of distributed vehicular broadcast (DV-CAST) protocol and pointed out safety specifications that are necessary for DV-CAST security against specific attacks. Several studies had implemented sinkhole attack detection and prevention on networks. The authors in [28] proposed an individual trust managing (ITM) technique to prevent against sinkhole attack in MANETs. The authors in [29] presented an approach to prevent the sinkhole attack in mobile ad hoc networks (MANETs). In [29], hop count-based detection techniques is used to detect sinkhole attack. The proposed solution to detect the sinkhole node utilizes the non-propagating route request techniques. The authors in [30] proposed memory effective node collusion method to prevent and detect sinkhole and wormhole attacks using a modified AODV protocol. [PERSON] et al., in [31], studied the multi-path multi-hop routing in networks with selfish nodes. The authors in [32] proposed an algorithm based on auction mechanism for vehicle routing problem to ensure that the auction could be used in operational decision making. However, these secure routing protocol in [26; 27; 28; 29; 30] established the secure route against sinkhole attack without auction theory, which leads to the additional process to detect the sinkhole node. Different from [26; 27; 28; 29; 30], the work [31; 32] proposed the auction theory-based secure routing protocols that did not require the sinkhole node detection process for the secure route establishment.