VANET based Cloud has evolved recently from traditional VANET (Vehicular Adhoc Networks) leveraging the power of cloud computing technologies. VANET based Cloud aims at disseminating reliable, accurate traffic information to VANET applications to make the transportation system safe. However, the Adhoc, decentralized nature of VANET, makes them attractive for security attacks. Since VANET is directly related to human lives, security and privacy issues are of paramount importance. Sybil attack is one such network layer attack observed in VANET, which completely disrupts the routing mechanism in network topologies, connections and increases the bandwidth consumption tremendously. This paper proposes AODV based cryptographic approach to disseminate secure traffic information resistant to Sybil attack in VANET.