中文摘要：

广义签密方案的最显著特点是能够实现加密、签名和签密3种功能.Liu等人构造了一个高效的无证书广义签密方案,并给出了正式的安全性证明;然而,文中通过构造具体的不可伪造性攻击算法,证明该方案对I类敌手不具备其所声称的不可伪造性.在不使用双线性映射的前提下,文中提出一个可证安全的高效无证书广义签密方案,并基于计算性Diffie-Hellman问题和离散对数问题的困难性,在随机预言机模型下对文中方案的机密性和不可伪造性进行了证明;由于文中方案具有安全、高效及无证书的优势,可广泛应用于秘密分发及安全通信等领域.

英文摘要：

Signcryption is basically a cryptographic primitive which provides both signature and encryption functions simultaneously, but it is not useful when only one of the function is required. Generalized signcryption is a special cryptographic primitive which can provide signcryption function when security and authenticity are needed simultaneously, and can also provide encryption or signature function separately when any one of them is needed. It is very suitable for storage- constrained environments. Liu et al. proposed an effective certificateless generalized signcryption scheme with formal security proof. However, specific unforgeable attack algorithm proves that it does not have the claimed unforgeability. Thus, this paper proposed a security certificateless generalized signcryption scheme with no bilinear pairings, and whose security is based on the hardness of the classical Computational Diffie-Hellman （CDH） problem and Discrete Logarithm （DL） problem under the random oracle model. Furthermore, performance analysis shows the proposed scheme is efficient and practical. Due to the advantage of being secure, effective and certificateless, this scheme can be widely used in such fields as secret distribution and security communication.