# Secure and Efficient High Throughput Medium Access Control for Vehicular Ad-Hoc Network
## 3 Secure VANET Communication (SVC) Using Commutative RSA Technique
Initialize the while loop and the options set of channels shared by vehicles. Initialize for loop for all shared vehicles in the network, and then, find if a vehicle belongs to the vehicle that shares their channel. If the channel is shared, then the assigned estimated throughput gain of the channel is zero; else, the vehicle computes throughout the gain considering the channel is allocated to vehicles. Assign estimated throughput gain for channel to the vehicle, and again, estimate throughput gain for the channel to the vehicle that shared the channel. If the estimated throughput gain is less than or equal to collision likelihood and overhead tradeoff, update overhead to 1 and set process to zero, and then, end the while. However, if the estimated throughput gain is greater than the collision likelihood, then provisionally allocates a channel to a vehicle that shares the available channel. Compute contention window and MAC overhead for the vehicle that shares the available channel. If the current MAC overhead is (minus initialized MAC overhead) greater than collision likelihood then, process overhead is set to 1. (Means it incurs MAC overhead as a result new channel need to be identified). Initialize the loop for all shared vehicles using updated MAC overhead. If the current MAC overhead is not greater than collision, then assign a channel to the shared vehicle. Compute MAC overhead and contention window and update group of channels shared by a set of vehicles. Update overhead to zero (no overhead is incurred in channel allocation of the shared channel) and increment the number of vehicles using the shared channel. However, the calculation of indicators is a very difficult task. Therefore, by taking MAC overhead \(\mathcal{D}<1\), we calculate the channel allocation throughput gain. (\(\mathcal{D}\) represents MAC overhead incurred in allocating a set of channels to the vehicle. The likelihood of collision due to the overhead incurred in the MAC layer due to channel allocation will be a range of 0 to 1.) Note: \(\mathcal{D}\) overhead is based on the output of the channel assignment. The calculation of \(\mathcal{D}\) is later described in the subsection of this paper. Consider \(y\) channel is the channel shared in \(x_{1},x_{2},\ldots,x_{\mathbb{T}}\) the vehicle, and \(\mathbb{T}\) are the sharing vehicles of \(y\) channel. Here, if the \(y\) channel is assigned to a particular \(x\) vehicle, then we compute the gain throughput of that vehicle. If other vehicles \(x_{1},\ x_{2},\ldots,x_{\mathbb{T}}\) do not use this \(y\) channel or are unreachable to the \(y\) channel, \(x\) vehicle can use the \(y\) channel which can increase throughput gain transmission when taken into consideration. The throughput gains of \(x\) vehicle and \(y\) channel are calculated as follows:  
\[\delta C_{x}^{\mathbb{T},b}(y)=\left(1-\frac{1}{\mathbb{T}}\right)(1-\mathcal{ D})l_{xy}\left(\prod_{o\in\mathbb{T}_{x}}\mathbb{\tilde{l}}_{xo}\right)*\left(1- \prod_{o\in\mathbb{T}_{x}}\mathbb{\tilde{l}}_{xo}\right)\sum_{n=1}^{\mathbb{T }}\left[\mathbb{\tilde{l}}_{xo}\left(\prod_{m=1,m\
eq n}^{\mathbb{T}}l_{xny} \right)\right] \tag{6}\]  
where \(b\) is the estimated throughput gain of user and channel; \(\mathbb{\tilde{l}}_{xo}\) is the number of users sharing the channel; \(1-\prod\limits_{o\in\mathbb{T}_{x}^{2}}\mathbb{\tilde{l}}_{xo}\) is the likelihood of the commonly shared channel users. \(s\) is the common shared channel; \(n\) is the shared channel user number; \(m\) is the user's number uses the shared channel; \(\prod\limits_{m=1,m\
eq n}^{\mathbb{T}}l_{xny}\) is the likelihood computation of throughput gain on a shared user channel. The \(\mathbb{S}\) - ENCCMA model is implemented using the RSA with the commutative key mechanism. \(\mathbb{S}\) - ENCCMA uses the ENCCMA real-time communication MAC protocol [37]. However, to provide access to real-time, ENCCMA combines Cognitive Radio, TDMA, and FDMA techniques. The ENCCMA MAC protocol can block signal transmission, and this aids to improve system efficiency.