In todays interconnected world, the idea of smart city is increasing rapidly, with vehicular ad hoc networks (VANETs) playing a vital role in facilitating smart transportation. In VANETs, vehicles frequently communicate with each other, allowing for real-time data sharing on vehicle location, speed, and road traffic conditions. This real-time data enhances traffic management, improves safety, and supports the overall efficiency of smart city transportation networks. But, due to the nature of open communication for VANETs, the exchange of information between the vehicles is public, and hence, it leads to severe security threats such as such as man-in-middle attack, replay attack, denial-of-services attack, impersonation attacks. Therefore, there is a need to implement flexible and scalable secure multifactor authentication technique to secure communication between the vehicles. This paper presents a secure multifactor authentication system based on Elliptic Curve Cryptography (ECC) and the Digital Signature Algorithm (DSA) within a software-defined VANET framework. Our proposed method is secure and better compared to existing methods due to its low computation cost, execution time, packet delivery ratio (PDR), and throughput.