Comments on “A Conditional Privacy-Preserving Certificateless Aggregate Signature Scheme in the Standard Model for VANETs”

In the paper "A Conditional Privacy-Preserving Certificateless Aggregate Signature Scheme in the Standard Model for VANETs" a pairing-based certificateless aggregate signature (CLAS) scheme was proposed. However, a malicious-but-passive KGC attack on this scheme was subsequently presented by Shim. In this paper, we show that even if the CLAS scheme is modified to prevent malicious-but-passive KGC attacks by incorporating Shim's countermeasure, there are still weaknesses that allow an adversary to forge aggregate or individual signatures.