# Secure and Efficient High Throughput Medium Access Control for Vehicular Ad-Hoc Network
## 3 Secure VANET Communication (SVC) Using Commutative RSA Technique  
This work presents a secure MAC protocol design for VANET. Firstly, we present a Perform Enriched Channel Algorithm (PECA) for the shared channel and the non-shared channel in VANET. First, we choose the best channel available to the user according to the throughput gain requirements. The users do not share channels here; the user enters the channel during a specified period and leaves the channel so that other users can access it. However, this algorithm cannot use the bandwidth effectively. This is because the channels are not shared. To solve this problem, the second algorithm proposes a shared channel allocation algorithm. Here, a group of users shares channels between neighboring users. This algorithm utilizes bandwidth efficiently, which aids in minimizing collision and maximize system throughput Then we present a CRSA based security design S \(-\) PECAfor secure communication among vehicles. The list of notations and symbols used in this paper is given in Table 2.  
\begin{table}
\begin{tabular}{c l l} \hline \hline \multicolumn{2}{c}{**Notations**} & \multicolumn{2}{c}{**Abbreviation**} \\ \hline \(x\) & Vehicle & \\ \hline \(C_{x}\) & Throughput Achieved & \\ \hline \(e_{xy}\) & Channel allocation decision & \\ \hline \(y\) & Channel & \\ \hline \(V_{x}\) & Channel set allocated to vehicle \(x\) & \\ \hline \(l_{xy}\) & The likelihood for channel \(y\) accessibility & \\ \hline \(1-\prod\limits_{y\in V_{x}}l^{\prime}_{xy}\) & The likelihood for channel \(y\) accessibility for at most one channelpt \\ \hline \(l^{\prime}_{xy}\) & The likelihood that channel \(y\) is not accessible \\ \hline \(\delta C_{x}\) & Throughput increment & \\ \hline \(V_{z}\) & The input set of accessible channels & \\ \hline \(C^{z}_{x}\) & Throughput before channel allocation \(y^{\prime}_{x}\). \\ \hline \(C^{q}_{x}\) & Throughput after channel allocation \(y^{\prime}_{x}\). \\ \hline \(T\) & Is the total number of channels in the network \\ \hline \(l^{\prime}_{xy}=1-l_{xy}\) & Is the probability of vehicle \(x\) not accessing the channel \(y\) \\ \hline \(y^{\prime}_{x}\) & channel allocation \\ \hline \(1-\prod\limits_{y\in T_{x}}l^{\prime}_{xy}\) & Is the probability of \(x\) vehicle accessing the channel \\ \hline \(\mathcal{D}\) & MAC Overhead \\ \hline \(\mathcal{V}\) & Number of vehicles \\ \hline \(\mathbb{T}\) & The sharing vehicles of channel \(y\) \\ \hline \(s\) & Is the common shared channel \\ \hline \(n\) & The shared channel user number \\ \hline \(m\) & Is the user’s number using the shared channel \\ \hline \(\prod\limits_{m=1,m\
eq n}^{T}l_{x_{xy}}\) & Is the likelihood computation of throughput gain on a shared user \\ \hline \(\mathcal{R}_{X}\)and \(\mathcal{R}_{Y}\) & The region member required to securely communicate over the \\  & secure channel \\ \hline \(j\) & Vehicle \\ \hline \(p_{j}\) & A set of channels shared by \(j\) \\ \hline \(F_{y}\) & Group of vehicles who share channel \(y\) \\ \hline \(P_{o}\) & A set of channels shared by \(o\) vehicle \\ \hline \(\mathcal{A}\) & contention window \\ \hline \(\mathcal{L}_{u}\) & Likelihood of the first collision \\ \hline \(\epsilon L\) & likelihood tradeoff \\ \hline \(r\) & No. of vehicles \\ \hline \(g\) & Arbitrary back-off time \\ \hline \(\mathcal{L}^{(r)}_{u}\) & Condition likelihood of the first collision \\ \hline \(\mathbb{L}\{r\text{ }vehicle\