基于扩展属性基功能加密的有效外包计算

针对目前属性基加密（ABE）方案存在的主要问题，即访问策略功能单一的问题和密文的大小和解密时间随着访问公式的复杂性增加而增长的问题，提出了有效外包计算的多功能ABE方案。首先，通过对敏感数据的细粒度访问控制，实现了不同功能加密系统；然后，利用云服务器巨大的计算能力进行部分解密计算，将满足访问策略的用户属性密文转化为一个（常量大小） ElGamal类型的密文；同时通过有效的验证方法保证外包运算的正确性。理论分析结果表明，与传统属性基功能加密方案相比，所提方案用户端的解密计算降低至一次指数运算和一次对运算，该方案在不增加传输量的情况下，为用户节省了大量带宽和解密时间。

Effecient outsourced computing based on extended attribute-based functional encryption

The main problems exist in current Attribute-Based Encryption (ABE) schemes, such as the access policy has a single function, and the size and decryption time of ciphertext increase with the complexity of access formula. In order to solve the problems, a multi-function ABE scheme for effecient outsourced computing was proposed. Firstly, through the fine-grained access control of sensitive data, different function encryption systems were implemented. Then, using the huge computing power of cloud server to perform partial decryption calculations, the user attribute ciphertext satisfying the access policy was converted into a (constant-size) ElGamal-style ciphertext. At the same time, the correctness of outsourced computing was ensured through the efficient verification methods. The theoretical analysis results show that, compared with the traditional attribute-based functional encryption scheme, the decryption computation at the user end of the proposed scheme is reduced to one exponential operation and one pair operation. The proposed scheme can save a lot of bandwidth and decryption time for users without increasing the amount of transmission.