In this paper, we study the physical layer security of multiple decode-and-forward cooperative vehicular to vehicular communications in which a known eavesdropper can receive the signals from source and relay nodes in the broadcast and cooperative phases, respectively. At first, we present a generalized optimal relay selection (GORS) in order to select the best relay considering the security of both broadcast and cooperative phases. Then, we apply an incremental mechanism to this generalized version, and propose an adaptive optimal relay selection (AORS) scheme which adaptively provides and preserves the security. Two scenarios are considered in the network based on availability of channel state information (CSI) of the main and wiretap links. For the first scenario where CSI is available at the receiver nodes, we analyze the secrecy outage probability and average spectral efficiency. Whereas, for the second scenario where CSI can be available at the transmitter node of each phase, the average secrecy capacity is analyzed. The results show that the AORS scheme can improve the secrecy performance compared to the GORS and Direct schemes. Moreover, the asymptotic analysis is provided which shows that the proposed scheme provides full secrecy diversity order. Finally, results of Monte Carlo simulations are presented that denote validity of the analysis and evaluate the system performance.

在本文中，我们研究了多解码转发协作车对车通信的物理层安全性，其中已知窃听者可以分别在广播和协作阶段接收来自源节点和中继节点的信号。首先，我们提出了一种广义最优中继选择（GORS），以便在考虑广播和合作阶段的安全性的情况下选择最佳中继。然后，我们将增量机制应用于这个通用版本，并提出了一种自适应最优中继选择（AORS）方案，该方案自适应地提供和保持安全性。基于主链路和窃听链路的信道状态信息 (CSI) 的可用性，在网络中考虑了两种情况。对于 CSI 在接收方节点可用的第一种情况，我们分析了保密中断概率和平均频谱效率。然而，对于CSI在每个阶段的发射机节点可用的第二种情况，分析了平均保密容量。结果表明，与GORS和Direct方案相比，AORS方案可以提高保密性能。此外，提供了渐近分析，表明所提出的方案提供了完全保密的分集顺序。最后，蒙特卡罗模拟的结果表明分析的有效性并评估系统性能。结果表明，与GORS和Direct方案相比，AORS方案可以提高保密性能。此外，提供了渐近分析，表明所提出的方案提供了完全保密的分集顺序。最后，蒙特卡罗模拟的结果表明分析的有效性并评估系统性能。结果表明，与GORS和Direct方案相比，AORS方案可以提高保密性能。此外，提供了渐近分析，表明所提出的方案提供了完全保密的分集顺序。最后，蒙特卡罗模拟的结果表明分析的有效性并评估系统性能。