Modern living is significantly impacted by intelligent transportation systems (ITS), which have the potential to alter how transportation is maintained and improve multiple facets of day-to-day mobility while also increasing security, effectiveness, and convenience. ITS offers the fundamental framework and technology necessary for IoV to operate efficiently. The IoV ecosystem foundation is the integration of sensors, communication networks, architectural components, and data analyses from ITS, which enables vehicles to join a connected, intelligent transportation network. Although ITS and IoV have many advantages, the increasing connectivity and data sharing also pose security risks, including those related to eavesdropping, authentication, privacy, and data integrity. To address these issues, we developed the novel, lightweight SAKM-ITS protocol, which enables authentication and key management between vehicles, roadside units (RSUs), and cloud servers. Using Scyther and Tamarin Prover tools, the protocol security is tested. For different attacks, an informal security study is also conducted. We also compared the findings with other recent computing and communication costs studies.