中文摘要：

结合无证书密码体制和签密思想提出了一个无证书代理重签密方案,在方案中,使用一个半可信代理人实现了一个签密到另一个签密的透明转换.与其他相似方案相比,实现了签密的完全转换.一般情况下,在Alice的私钥和Bob的公钥下完成的签密经转换后只能用Alice的身份信息和Daddy的私钥解签密;在本文提出的方案中,由Alice的私钥和Bob的公钥完成的签密经转换后可以用Charlie的身份信息和Daddy的私钥解签密,且签密的验证不需要明文信息的直接参与.基于间隙双线性Diffie-Hellman问题,在随机预言机模型下,证明了可以抵抗无证书代理重签密中的第一类攻击.

英文摘要：

A certificateless proxy re-signcryption scheme is advanced by combining certificateless cryptosystem with signcryption. In this scheme, the transparent conversion from one signcryption to another is achieved by utilizing a semi-trusted proxy. Compared with the other similar schemes, this scheme realizes the complete conversion of sign- cryption. Generally, after the signcryption under the private key of Alice and the public key of Bob is converted, it can only be de-signcryted by using the identity information of Alice and the private key of Daddy. However, in the scheme advanced in this paper, not only can the identity information of Charlie and the private key of Daddy de-signcrypt the converted signcryption under the private key of Alice and the public key of Bob, but also the verification of signcrytion does not involve the direct participation of plaintext. Based on the GBDH problem, it can be proved that this scheme can resist the first kind of attacks in certifieateless proxy re-signcryption under the Random Oracle Model.