Security Enhanced CLS and CL-AS Scheme Without Pairings for VANETs

While vehicle ad-hoc networks (VANETs) have many advantages, they also present privacy and security concerns. Certificate management issues have been seen in traditional public key infrastructure-based privacy-preserving authentication schemes, while key escrow problem exists in identity-based privacy-preserving authentication techniques. Also, existing cryptographic techniques rely heavily on assumptions about tamper-proof equipment to ensure their security. A proposal has been made for a certificateless aggregate signature system for VANETs addressing these issues and was proved provably unforgeable against collusion attack. However, we found that the proposed technique was insecure and could not withstand collusion assault. Therefore, this paper presents an improved and secure certificateless aggregate signature technique for VANETs. We also illustrate the security & performance evaluation of our presented technique, and based upon the hardness assumption of the elliptic curve discrete logarithm problem, we have shown that the technique is safe against existential forgery on adaptive chosen message attack in the random oracle model. Also, the presented technique has better efficiency compared to some recent existing authentication techniques.