Vehicular Ad-hoc Networks (VANETs) are a type of Internet of Things system where groups of vehicles communicate with each other and traffic monitoring infrastructure in order to provide safety and quality of life improvements for drivers and others in the area. Vehicles in a VANET are responsible for reporting their own status, as well as the statuses of the roadway, traffic, and environment in their immediate vicinity, to the system controller and other drivers for processing. VANET systems are open to the public, with vehicles joining and leaving at a high rate. This feature results in two high-priority requirements for VANET security: vehicles in a VANET must be held responsible for the correctness of the information that they report, and schemes ensuring message security must be quick. This paper presents an efficient, pairingfree signature scheme for VANETs that prevents the forgery of signer identities, including in the case of insider attacks, without the use of a tamper-proof device.