T he signcryption scheme proposed by Zhang Jian‐hang et al is analyzed , and the scheme don’t have the forward security . An improvement scheme is proposed with public verifiability and forward security , the correctness and security are proved . The efficiency of the scheme is increased significantly compared with two existing schemes . Moreover , a new signcryption scheme based on elliptic curves is proposed with public verifiability and forward security . In the algorithm , both the numbers of model multiplication and model inverse are reached the minimum four times and zero times , the efficiency of the algorithm is increased significantly compared with the existing signcryption scheme .%指出张建航等提出的数字签密方案无前向安全性，提出了一个新的可公开验证和前向安全的数字签密方案，并进行了正确性和安全性分析，与已有方案比较，降低了算法复杂度。同时，指出张建航等提出的椭圆曲线数字签密方案复杂度过高，给出了一个新的签密方案，方案具有前向安全性和公开验证性，模乘运算达到最小值4次，模逆运算达到最小值0次，复杂度达到理论最小值。
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