By analyzing the first generalized threshold signcryption scheme (WCL scheme) and its improved schemes (TJC scheme, etc.), it was found that they can’t resist several attacks such as equation attack and can’t realize threshold designcryption. In order to remedy their security flaws, a novel security enhanced generalized threshold signcryption scheme was presented. In the new scheme, the random factor was added to the secret parameter R so as to completely realize the function of generalized threshold signcryption, i.e.(t,n)threshold signcryption and(k,l)threshold designcryption, and by means of Chaum-Pedersen discrete logarithm equation knowledge protocol, malicious members’deceitful behaviors could also be detected. Security analysis and efficiency evaluation showed that this new scheme could resist all the attacks proposed in previous literatures and was more efficient than WCL scheme with respect to computation and communication costs.
