自认证签密方案的安全性研究

Safety of self-certified signcryption scheme

签密体制是将签名和加密融为一体的思想,它改变了传统的先签名后加密的体制,而是在一个逻辑步骤内实现对传送信息的既保密又认证的服务。设计安全、高效的签密方案非常重要。对现存文献进行分析,发现有些方案存在不同程度的安全缺陷,它们不满足不可伪造性:即存在已知明文与密文对的伪造攻击,任何第三方均可借助窃取到的明文与密文对假冒签密者伪造任意消息的合法签名,严重危害签密者的利益。

Signcryption scheme is an integration of signcrypted signature and encryption system, which is different from the traditional first-signature-and-then-encryption system, and which achieves both confidential and certified services for the transferred information within a logical step. Thus how to design a safe and efficient signcryption scheme is particularly important. We analyze the security flaws in the existing literature which do not meet unforgeable requirement, that is, there is a known forgery at- tack against the plaintext and ciphertext. Any third party can steal plaintext and ciphertext,and counter- feit signcrypter legitimate signatures for any messages,which seriously harms the interests of signcrypt-ers.