On the security models for certificateless signature schemes achieving level 3 security

Public key cryptography has found many applications in our modern society. To guarantee the authenticity of public keys, we need a trusted third party (TTP). In 1991, Girault defined three trust levels for a TTP. The higher the trusted level of the TTP is, the higher the security level of the cryptographic scheme is. In 2007, Hu et al. proposed a generic construction of a certificateless signature scheme, together with a security model, achieving Girault’s level 3 security. In 2011, Fan et al. presented a certificateless short signature scheme based on pairings. In this paper, we consider in depth the security requirements of certificateless signature schemes and show that previous models are inappropriate for achieving the desired level of security. We also present a new security model for a certificateless signature scheme to achieve level 3 security.