中文摘要：

前向安全在实际应用中能有效减少私钥泄露对过去时间段签名带来的损失,但会影响未来时段签名的安全性。针对未来时间段的私钥泄露问题,提出了一种强前向安全的数字签名方案。先是对刘亚丽（2010）等提出的基于模m的n方根难题的ElGamal前向安全数字签名方案进行了分析,发现该方案并不能保证未来时间段签名的安全性,即不具备后向安全。于是借助单向散列链技术对该方案的私钥更新和签名算法进行了有效改进,在刘亚丽所提方案的基础上构造了一种基于ElGamal体制的数字签名方案,并对该方案进行了分析。分析结果表明,新方案是正确有效的,同时具有前向安全性和后向安全性。

英文摘要：

Forward security can effectively reduce the damage caused by exposure of the secret key in the past time period, but may affect the signature in the future period. In order to solve this problem, a strong forward-secure signature is proposed. Firstly, Liu Yali＇ s ElGamal forward-seem signature scheme in 2010 based on n root of module m is analyzed,and this scheme is not backward security,which means it can＇ t guarantee the signature security in the future period. Then, by using a one-way hash chain, the key updating and signature algorithm is improved effectively. A new digital signature scheme based on ElGamal is presented on the basis of Liu＇ s scheme and ana- lyzed. The result shows that the new scheme is correct and feasible, with forward and backward security.