Abstract: To satisfy the requirement for multi-keyword searching over encrypted data, and solve the problem of privacy preserving and data security of the users, a modified multi-keyword ranked searchable encryption scheme is proposed. The scheme utilizes the vector space model to construct the searchable index and uses the improved homomorphic encryption algorithm to encrypt and decrypt data. It also supports the ranked result, which effectively avoid returning the low relevance documents. Further thorough security analysis and performance evaluations show that the scheme provides [CCA2]security and how effectively improves system performance and reduce communication cost and eliminates unnecessary traffic.

Key words: multi-keyword ranked search, hommomorphic encryption, vector space model, cloud computing

摘要： 为满足加密文件的多关键字检索需求并解决云存储下用户的隐私与数据安全的问题，提出改进的分级的多关键字可搜索加密方案。该方案保障数据与查询机密性的同时，利用向量空间模型构建可搜索索引，使用同态加密算法进行加解密，支持查询结果的分级检索，有效避免了服务器端返回相关度不大的文件。进一步的安全分析和性能评估表明，该方案在安全性上满足[CCA2]安全，降低了通信开销，也消除了不必要的流量开销。

关键词: 多关键字分级检索, 同态加密, 向量空间模型, 云计算