Insecurity of a Certificateless Signature Scheme

Certificateless signature scheme delivers the certificate problem and solve the key escrow problem inherit in the public key cryptography and identity based cryptography. Xiong et al suggested a certificateless aggregate signature scheme and proved that their CLS scheme is protected against all adversaries present in the network. Yang et al found that Xiong et al CLS scheme was not protected against type 2 adversary and proposed an improved CLS scheme. In this paper, during we demonstrate that Yang et al designed CLS scheme is unconfident beside type 2 adversary attacks.