A Modified Efficient Certificateless Signature Scheme without Bilinear Pairings

Certificateless public key cryptography was proposed to solve the key escrow problem in identity-based public key cryptography. Namely, a user´s full private key must be comprised of a partial private key which is provided by the key generation center and a secret value which is chosen by the user. Thus the key generation center can no longer acquire each user´s full private key by itself. In 2014, Yeh et al. proposed an efficient certificateless public key signature scheme without bilinear pairings. They also showed their scheme is secure against super adversary under the hardness of breaking discrete logarithm problem in the random model. In this paper, we modify Yeh et al.´s scheme to obtain a new scheme which is more practical than theirs. And our modified scheme can achieve the same security level as Yeh et al.´s scheme under the hardness of breaking discrete logarithm problem in the random model.