Abstract: The users may dynamically enter or leave the Personal Health Record（PHR） system, so the realtime fine-grained attributes revocation is required and is more suitable for practical applications. In this paper, an improved weighted attribute-based encryption scheme with revocation is proposed. The proposed scheme not only has the function of out sourcing decryption, but also does fine-grained attributes revocation in time. By constructing the KEK tree, the proposed scheme updates key and cipher text timely to achieve fine-grained attributes revocation. In addition, based on the fact that the importance of the attributes is not considered in existing policy attributes ciphertext encryption schemes, the concept of weight attribute is adopted in the proposed scheme to make it more suitable for the PHR system. The security analysis and experimental results indicate that, compared with existing CP-ABE schemes, the proposed scheme resists the conspiracy attack, ensures the confidentiality of data, and guarantees the forward and backward security. In addition, the computational complexity of the propopsed scheme is decreased.

Key words: Personal Health Records（PHR） system, attribute revocation, weighted attribute, attribute-based encryption

摘要： 在PHR（Personal Health Records，个人健康记录）系统中，用户会动态地加入或离开，及时撤销细粒度的属性更加适用于实际应用系统。为此，提出一种改进的基于仲裁者的密文策略的属性基加密方案，使其能够在具有外包解密的同时可以实现细粒度属性及时撤销。该方案通过构造KEK树及时更新密钥和密文以此来及时撤销细粒度属性。此外，针对现有的密文策略属性基加密方案较少考虑到属性重要性，将属性权重的概念引入该方案中，使其更加适合PHR系统。安全性分析和仿真实验表明，与已有方案相比，所提方案可以抵抗合谋攻击，保证数据机密性以及前向安全和后向安全。此外，该方案具有更低的计算复杂度。

关键词: 个人健康记录（PHR）系统, 属性撤销, 属性权重, 属性基加密