属性基加密方案被认为是云存储环境下数据资源访问控制的最佳选择,但是策略更新很大程度上限制了其在实际中的应用.针对此问题,提出一种支持策略动态更新的多机构属性基加密方案.该方案引入匿名密钥分发协议为用户生成私钥,有效地保护用户的隐私,并抵抗属性机构的共谋攻击.另外,方案采用动态策略更新算法,支持任何类型的策略更新,大大减少传统策略更新中的计算和通信开销.经安全性分析证明,方案在标准模型下满足自适应选择明文攻击安全.通过对比,用户私钥和密文长度都有所减少,密文更新交给云服务器完成,降低了数据拥有者的工作量,更加贴近实际应用.%Attribute-based encryption (ABE) is a new cryptographic technique which guarantees fine-grained access con-trol of outsourced encrypted data in the cloud environment. However, a key limitation remains, namely policy updating. Thus, a multi-authority attribute-based encryption scheme with policy dynamic updating was proposed. In the scheme, an anonymous key issuing protocol was introduced to protect users' privacy and resist collusion attack of attribute authority. The scheme with dynamic policy updating technique was secure against chosen plaintext attack under the standard model and can support any types of policy updating. Compared to the existing related schemes, the size of ciphertext and users' secret key is reduced and can significantly reduce the computation and communication costs of updating ciphertext. It is more effective in the practical application.
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