To overcome the latency issue in real-time communication, a number of research based solutions and architectures are being proposed. In all these, security is not considered an important factor since it causes extra delay in the communication and introduces overhead. Therefore, a design decision is needed to assess tradeoff between efficiency and security mechanisms. In this respect, we designed a security approach in Software Defined Networks (SDN) based Vehicular Autonomous Ad hoc Network (VANET) where low latency and security are essential elements. VNAET provides a system of systems approach where various hybrid solutions are integrated and installed on number of network nodes managed by SDN. In such networks, our novel approach exchanges security context in a synchronized manner to serve as a baseline for network nodes to dynamically adopt security features as per security requirements of these nodes. Hence, various security contexts are designed and categorized based on the nature of information exchange between nodes, mainly, to offer authentication, secure and trustworthy communication services. These well-designed security contexts enable devices of different capabilities to securely communicate by using predefined security parameters and cryptographic functions. This eliminates the need to negotiate any secure communication parameters and hence results in less communication overhead. In addition, our approach is integrated with verifiable identities (Veidblock) concept which addresses privacy issues through anonymity. These security contexts are verified by using scyther by demonstrating that the trustworthiness is achieved by countering non-repudiation, impersonation, tampering, eavesdropping and replay attacks.