Comments on an identity-based signature scheme for VANETs

In this letter, we analyze the identity-based signature with conditional privacy-preserving authentication scheme (short for IBS-CPPA, published in Journal of Systems Architecture, doi: 10.1016/j.sysarc.2019.101692 ) and demonstrate that it cannot provide secure authentication between vehicles. Specifically, in IBS-CPPA, two types of adversaries can launch different attacks to forge a valid signature on any traffic-related message to impersonate a target vehicle, so as to invalidate the authentication between vehicles.