Security Analysis of Conditional Privacy-Preserving Authentication Schemes for VANETs

In order to solve security and privacy-preservation issues in VANETs, a number of conditional privacy-preservation schemes based on certificateless signature (CLS) schemes and certificateless aggregate signature (CLAS) schemes have been proposed. However, most of them were insecure against several types of attacks. Recently, Wang et al. and Xiong et al. proposed new conditional privacy-preserving authentication schemes based on CLAS and CLS schemes, respectively, for VANETs. We present malicious-but-passive KGC attacks on Wang et al.’ scheme, and forgery attacks and key recovery attacks on Xiong et al.’ scheme, where KGC or anyone can generate valid signatures on any messages for any vehicles without being traced by TA. Our attacks break their unforgeability and traceability. At last, we discuss their causes and countermeasures.