云计算中基于属性和定长密文的访问控制方法

随着云计算应用的增加，安全问题引起了人们的高度重视。由于云计算环境的分布式和不可信等特征，数据属主有时需要对数据加密后再托管云存储，如何实现非可信环境中加密数据的访问控制是云计算技术和应用需要解决的问题。文中提出一种基于属性和固定密文长度的层次化访问控制方法，该方案将密文长度和双线性对计算量限制在固定值，具有较高的效率，并且引入层次化授权结构，减少了单一授权的负担和风险，实现了高效、精细、可扩展的访问控制。同时证明了该方案在判定性q-BDHE假设下具有CCA2安全性。

Access Control Method Based on Attribute and Constant-size Ciphertext in Cloud Computing

With the popularity of cloud computing ,there have been increasing concerns on its security. Data owners have to encrypt outsourced data to enforce confidentiality as the cloud computing environment is distributed and untrusted. Therefore,how to achieve practicable access control of encrypted data in untrusted environment is an urgent issue to be solved. Propose a hierarchical attribute-based access control scheme with constant-size ciphertext. The scheme is efficient because of the constant-size ciphertext and computation cost in encryption and decryption algorithms. Furthermore the hierarchical authorization structure which reduces the burden and risk in the case of one single authority makes it scalable. At the same time,prove that the scheme is of CCA2 security under the decisional q-Bilinear Diffie -Hellman Exponent assumption.