支持直接撤销的固长密文策略属性基加密方案

该文提出一种支持直接撤销功能且具有固定长度的密文策略属性基加密方案，首先给出了该属性基加密方案的形式化定义和安全模型，然后对方案具体的实现进行了阐述，最后给出了该方案在标准模型下的安全性证明。该方案在密文长度和解密开销固定的同时，允许用户在加密过程中将撤销列表嵌入到密文中以实现直接撤销，保证了仅当用户所拥有的属性满足密文访问结构且用户身份没有出现在撤销列表的前提下，才可以使用自己的私钥解密执行解密。对比分析结果表明，该方案较同类方案具有更高的计算效率且支持更灵活的访问结构。

Direct Revocable Ciphertext Policy Attribute-Based Encryption Scheme with Constant-Size Ciphertext

By considering the dynamic user access privilege and the potential leakage of secret key, a direct revocable ciphertext policy attribute-based encryption (usually shorten as CP-ABE) scheme with constant-size ciphertext is proposed in this paper. Different from the indirect revocable CP-ABE, the proposed approach allows the data owner to assign the revoked users during the encryption without interacting the attribute authority periodically. The definition and security model of the direct revocable attribute-based encryption scheme are given and a concrete scheme is also constructed correspondingly. The security proof of the scheme is given under the standard model. The results of comparative analysis show that the scheme achieves higher computational efficiency and supports more flexible access structure than the state-of-the-art.