Practical modification of an efficient public-key framework

J. Zhou proposed a new public-key framework, in which the maximum lifetime of a certificate is divided into short periods and the certificate could expire at the end of any period under the control of the certificate owner (or his manager in a corporate environment). However, Zhou´s public-key framework is not suitable on implementation in real world. Therefore, we review some security parameters and change them into more suitable ones for implementation. Moreover, we remove an unnecessary trust party of Zhou´s public-key framework and propose an improved scheme for realistic solution.