Due to the hybrid architectural design and dynamicity, security is a big concern in VANETs. The major security concerns are authentication, privacy, confidentiality, and integrity. The security mechanisms provide a strong defense against security attacks using authentication keys and certificates. Also, it assists in discarding the malicious messages from the VANET based dissemination models. The VANET security mechanisms are categorized into key-based solutions, certificate-based solutions, and trust-based solutions.