Vehicular Ad hoc Network (VANET) is considered as an essential component of Intelligent Transport system. VANET has gained an ample amount of attention from the researchers and automobile industry. Security and privacy are the primary requirements in the successful deployment of vehicular communication in VANET. Lack of security and confidentiality in VANETs is the primary barricade in the successful deployment of VANET. To establish trust within the entities participating in VANET operations is the primary aim of VANET security and play a vital role in prevention of attack in VANET. This paper describes a comprehensive identity authentication scheme (CIAS) based on asymmetric encryption that facilitates the authentication for Vehicle-to-Infrastructure (V2I) and inter RSUs. The proposed scheme is validated by extensive simulations and compared with the related works on the basis of communication overhead (CO), Latency and packet delivery ratio (PDR). The result of simulations shows that proposed authentication scheme outperforms.