In order to overcome the flaw in the Xiao scheme on conic curve over Zn, of which the published parameter Nn could make it possible that the modulus n could be factorized, an improved scheme was proposed here. In our proposed scheme, the parameter Nn was kept secretly, and the verifying algorithm was presented. Moreover, generalized conic curve was chosen to replace conic curve. The security analysis showed that the improved scheme is easy to accomplish for convenient embedding plaintext, computing element order and points in the generalized conic curve. In addition, this scheme is a digital signature scheme based on computing discrete logarithm and factorizing great integer, and has more curves for choice than it on conic curve.
