With the advent of electric vehicles (EVs) and the proliferation of vehicle technologies like drive-by-wire and autonomous driving, advanced communication protocols to connect vehicles and the infrastructure have been proposed. However, practical large-scale deployments have been hindered due to caveats such as hardware, and infrastructure demands — including the security of vehicles, given their ubiquitous nature and direct correlation to human safety. As part of this thesis, we look at deploying a practical solution to adopt a secure large-scale vehicle-to-everything (V2X) communication architecture. Then, we also try to analyze and detect vulnerabilities in vehicle-to-grid communication for electric vehicles. In the first work, we analyze, build a proof of concept and evaluate the use of commercial off-the-shelf (COTS) smartphones as secure cellular-vehicle-to-everything (CV2X) radios. Here, we study the various possible network topologies considering the long-term evolution (LTE) technology with necessary latency requirements considering security and the associated overhead. We further simulate the proposed method by considering real-world scalability for practical deployment. In the second work, we analyze the ISO15118 standard for EV-to-electric grid communication involving high levels of energy exchange. We develop a grammatical fuzzing architecture to assess and evaluate the implementation of the standard on a road-deployed vehicle to detect security vulnerabilities and shortcomings. / Master of Science / The technology around vehicles and the transportation infrastructure has immensely advanced in the last few decades. Today we have advanced technologies like driver assistance, automated driving, and access to multimedia within our vehicles. And deploying such technologies has only been possible due to advancements in the electronics embedded in the vehicles and surrounding infrastructure. Opportunely, we can further improve the technologies to include numerous safety features by connecting vehicles and infrastructure via communication networks. However, this poses immense challenges regarding the scaling of communication infrastructure for the timely exchange of data and its security. But, given the proliferation of cellular technology, the ubiquitous nature of smartphones, and their capabilities, we propose and evaluate the idea of using commercial off-the-shelf (COTS) smartphones to connect vehicles and the infrastructure to exchange data securely. The first work of this thesis details the analysis and evaluation of the system and the network for a secure COTS-based cellular-vehicle-to-everything architecture, including a proof of concept hardware implementation and additional simulations. Additionally, in light of climate policies and cleaner transportation alternatives, we are moving from gasoline-based internal combustion engines to electric vehicles, requiring the transfer of extended amounts of electric energy from the electric grid to the batteries in the vehicles. In light of the same, ISO 15118 standard was developed to reduce repetitive efforts and standardize the communication and exchange of this energy. But as with any new technology, especially involving communication, new attack vectors for malicious entities open up. Therefore, we study this new standard and develop a novel fuzzing architecture to test the implementation of the standard on deployed real-world vehicles for security vulnerabilities and robustness. Again, as this is a nascent technology and standard, a fuzzing approach would accelerate the detection of edge cases and threats before these are exploited to cause harm to human life and property.