In this paper, two improved digital signature schemes are presented based on the design of directed signature scheme [3]. The peculiarity of the system is that only if the scheme is specific recipient, the signature is authenticated. Since the scheme adds the screen of some information parameters, the difficulty of deciphered keys and the security of digital signature system are increased. In this paper, two improved digital signature schemes are presented based on the design of directed signature scheme [3]. The peculiarity of the system is that only if the scheme is specific recipient, the signature is authenticated. Since the scheme adds the screen of some information parameters, the difficulty of deciphered keys and the security of digital signature system are increased.