Abstract:At present, the security of the identity based proactive threshold signature schemes was almost proved in the random oracle model, and the threshold values of these schemes were almost changeless. Aiming at this two problems, a proactive threshold signature scheme was presented by using the hardness of the computational Diffie-Hellman problem with no trusty center and changeable threshold value, based on the modification of Paterson’proposed identity based signature scheme. The scheme’s correctness was exactly proved in terms of bilinear pairing technique and its security was analyzed and proved in detail in the assumption of the computational Diffie-Hellman problem.