Cryptanalysis and Improvement for Certificateless Aggregate Signature

In order to satisfy application in resource constrained environment, aggregate signature schemes have been widely investigated. Recently, He et al. pointed out that certificateless aggregate signature (CLAS) scheme proposed by Xiong et al. was insecure against the Type II adversary and presented an possible improvement. In this article, we show that their improved scheme is not secure against a malicious-but-passive KGC attack. We analyze attack reason and propose an improved certificateless aggregate signature scheme. Based on the CDH difficult problem assumption, the proposed CLAS scheme is existentially unforgeable against adaptive chosen-message attacks in the random oracle model.