中文摘要：

在无证书公钥密码体制下研究代理重加密技术,给出无证书代理重加密系统的形式化定义与安全模型,构建一个新的无证书代理重加密方案,并在随机预言模型下证明其在适应性选择明文攻击下是安全的。基于该方案,云服务商可利用用户提供的代理钥,将待分享的加密数据转换为针对其他用户的密文,其他用户采用自身私钥进行解密并访问原始数据,达到共享数据的目的。分析结果表明,该方案能够有效保证云环境下数据存储与共享的安全性及可靠性。

英文摘要：

This paper researches Proxy Re-encryption （PRE） technology under the Certificateless Public Key Cryptography （ CL-PKC）, gives a formal definition and security model for certificateless PRE system and construct a new certificateless PRE scheme. The new scheme is proved secure against chosen plaintext attack in the Random Oracle Model （ROM）. With the help of the proposed scheme, cloud service providers can transform cipbertexts encrypted under a user＇ s public key into different ciphertexts that can be decrypted by the other user＇ s secret key, and the other user also can access raw data to realize data sharing. Analysis result shows that the scheme can effectively ensure the safety and reliability of data under the environment of cloud computing.