Attribute based encryption is an effective method which can solve the access control problem of cloud storage. Realizing both efficient attributes revocation and outsourcing decryption would enhance mobile user experience. In this paper, we present a new scheme of Key-Policy Attribute Based Encryption in hybrid cloud system. In our scheme, the most of computation in the decryption process can be outsourced to the cloud and the efficiency of system is improved. In addition, the attributes of malicious users or expired ones can be revoked with unrelated users offline. Moreover system consumes a little resources rather than rebuilds the system or updates all data immediately. We also give a proof of security, a detailed description of execution and efficiency analysis.

基于属性的加密是解决云存储访问控制问题的有效方法。同时实现有效的属性撤销和外包解密将增强移动用户的体验。本文提出了一种基于密钥策略属性的混合云系统加密新方案。在我们的方案中，解密过程中的大部分计算都可以外包给云，从而提高了系统效率。另外，恶意用户或过期用户的属性可以通过不相关的用户脱机来撤消。此外，系统会消耗一些资源，而不是立即重建系统或更新所有数据。我们还将提供安全性证明，执行和效率分析的详细说明。