Provably secure certificate-based signature scheme without pairings

In order to simplify certificate management in traditional public key cryptography and solve the key escrow problem in identity-based cryptography, the notion of certificate-based cryptography was introduced. Recently, Ming and Wang proposed a certificate-based signature scheme without pairings. They claimed that the scheme was existentially unforgeable against adaptive chosen message and identity attacks in the random oracle. In this paper, we show that the scheme is insecure against a malicious certifier under existing security model. We also propose a new efficient certificate-based signature scheme without pairings, which is proven secure in the random oracle model. Compared with the existed certificate-based signature schemes without parings, our scheme enjoys shorter signature length and less operation cost.