Cryptanalysis and Efficient Improvement of a Robust and Scalable One-Way Hash Chain Authentication Protocol in Vehicular Communication

Recently, a hash-chain based authentication protocol has been proposed, named HAP, in vehicular communications to improve the scalability. By means of removing certificate cost, HAP earns a great performance in terms of computational overhead and message loss ratio. Unfortunately, we discover a fatal security flaw that malicious vehicles can masquerade as an innocent one to disseminate forged messages, which contradict to the security claims of HAP. This study tries to use the least effort to mend the severe security leak. We deliberately strengthen the security level of HAP by only adding a random number in registration phase without any harm to its excellent performance result.