Security analysis of a provably secure identity-based signature scheme using bilinear parings

In 2009, J. Li and P. Jiang proposed a provably secure identity-based signature scheme using bilinear pairings, which is claimed secure in the standard model. However, we present that any attacker can forge the private key of an identity or a signature if the second part of an identity's private key is not certificated by the Private Key Generator (PKG). Therefore, the signature-based binding of the identity and the private key must be adopted to improve this scheme's security.