  Wireless communications form the backbone of future vehicular networks,
playing a critical role in applications ranging from traffic control to
vehicular road safety. However, the dynamic structure of these networks creates
security vulnerabilities, making security considerations an integral part of
network design. We address these security concerns from a physical layer
security aspect by investigating achievable secrecy rates in wireless vehicular
networks. Specifically, we aim to maximize the sum secrecy rate from all
vehicular pairs subject to bandwidth and power resource constraints. For the
considered problem, we first propose a solution based on the successive convex
approximation (SCA) method, which has not been applied in this context before.
To further reduce the complexity of the SCA-based method, we also propose a
low-complexity solution based on a fast iterative shrinkage-thresholding
algorithm (FISTA). Our simulation results for SCA and FISTA show a trade-off
between convergence and runtime. While the SCA method achieves better
convergence, the FISTA-based approach is at least 300 times faster than the SCA
method.
