Cryptanalysis of some certificateless signature schemes in the standard model

Certificateless Public Key Cryptography, which removes the necessity of certificate to ensure the authentication of the user's public key in the traditional Certificate-Based Public Key Cryptography and also overcomes the inherent key escrow problem in the Identity-Based Public Key Cryptography. So far, to the best of our knowledge, in the literature there are only five certificateless signature schemes without additional properties, whose security can be proved in the standard model. However, we show attacks to some of these five schemes and conclude that all of them are insecure. Particularly, we show two types of attack on a certificateless signature scheme in the standard model which is very recently proposed by Yu et al.. Finally, we leave how to design an efficient and provable secure certificateless signature scheme without additional properties in the standard model as an open problem.