Abstract: The paper presents that a certificateless signcryption scheme proposed recently is easily attacked by public key replacements, and then points out the relevant attack instances. A new certificateless signcryption scheme without bilinear pairings is also proposed in this paper. Cryptography is executed in entities’ certificateless public key authentication and escrow public key authentication separately, which ensure that the new scheme would not experience the similar public key replacement attacks. In the standard model, the new scheme is verified secure, and the new scheme can achieve the unforgeability and confidentiality of certificateless signcryption. Comparative analysis shows that the new scheme not only ensure strong security but also better computing performance.

Key words: certificateless signcryption, bilinear pairing, unforgeability, confidentiality, public key replacement attack

摘要： 首先指出近期提出的一种无证书签密方案易受到公钥替换攻击，并给出了相关攻击实例。进而提出一种新的无双线性对的无证书签密方案，通过对实体的无证书公钥和托管公钥进行独立的密码学验证，确保了新方案不遭受与现有方案类似的公钥替换攻击。在标准模型下，新方案被证明是安全的，能够实现无证书签密的不可伪造性和机密性。对比分析表明，新方案在确保强安全性的同时具有较好的计算性能。

关键词: 无证书签密, 双线性对, 不可伪造性, 机密性, 公钥替换攻击