电子商务签密方案的改进与安全性分析

摘要

首先介绍了数字签密与传统的“签名+加密”的方法相比所具有的优势,并给出了构成数字签密方案的四个子算法.然后简要介绍了签密方案涉及到的数学基础,并对现有的几种标准模型下的基于身份的数字签密方案进行了回顾,对Yu等所提方案的安全性进行了分析,指出它在挑选密文攻击方面是不安全的.接下来提出一种改进的数字签密方案,分别对构成该方案的系统建立、密钥提取、数字签密、解签密四个子算法进行了分析.从适应性选择消息下的不可伪造性和选择密文攻击下的密文不可区分性两个方面对方案的安全性进行了简要的说明.最后对改进方案的效率与其它几种方案进行了比较,得出了改进的方案在密文长度等方面存在一定优势的结论,并提出了下一步的研究计划.%Firstly,the paper presents the advantage of digital signcryption over the traditional "signature+encryption" method,and describes the four sub-algorithms which compose the digital signcryption scheme.Secondly,it briefly introduces the mathematical basis of the digital signcryption,reviews several existing identity-based digital signcryption schemes under the standard model.It analyses the security of the digital signcryption scheme designed by Yu,and points out that it is insecure when it is attacked by select ciphertext.Thirdly,it gives an improved digital signcryption scheme,and respectively analyses the digital signcryption scheme consisting of four sub-algorithms-the system establish algorithm,the key extraction algorithm,the digital signcryption algorithm and the unsigncryption algorithm.The scheme's security is briefly described through the two aspects of unforgeability under adaptive select message and ciphertext indistinguishability under select ciphertext attack.Finally,the paper compares the efficiency of the improved scheme with other schemes,concluding that the improved scheme is superior at ciphertext size etc,then puts forward plans for future research.