Hybrid conditional privacy-preserving authentication scheme for VANETs

In existing authentication schemes for vehicular ad hoc networks (VANETs), the public key infrastructure (PKI)-based pseudonym certificate, identity-based encryption and group signature technology are usually used to preserve the security and privacy. However, these schemes face some challenges, e.g., the time-consuming certificate revocation list (CRL) checking, identity revocation issue and the computation overhead of group signature, respectively. To cope with these challenges, we propose a hybrid conditional privacy-preserving authentication protocol based on the PKI certificate and identity-based signature. In our scheme, the trust authority (TA) assigns the unique long-term certificate for every registered node. Only the vehicle with valid certificate can apply the anonymous short term identity from the current RSU to sign safety-related message. The identity-based signature avoids the CRL checking and the complex bilinear paring operation. When vehicle is compromised, TA can easily revoke its identity by the only long-term certificate. To further enhance efficiency, vehicle can verify the received messages by the single or batch authentication manner. In addition, we optimize the authentication process to avoid vehicle verifying the repeated and unnecessary signatures. Compared with the current schemes, the simulation result shows that our authentication protocol can effectively reduce verified messages in the case of meeting the requirement of security and privacy.