Abstract: Since existing dynamic multi-keyword ranked search schemes over encrypted data in cloud storage can not support semantic extension and do not have forward and backward security, a multi-keyword ranked search scheme over encrypted cloud data was proposed, which supported semantic search and achieved forward and backward security. The semantic extension of query keywords was achieved by constructing semantic relationship graph, the retrieval and dynamic update of data were achieved by use of tree-based index structure, the multi-keyword ranked search was achieved based on vector space model, and the extended index and query vectors were encrypted by using secure K-nearest neighbor algorithm. Security analysis indicates that the proposed scheme is secure under the known ciphertext model and achieves forward and backward security during dynamic update. Efficiency analysis and simulation experiments show that this scheme is superior to the same type schemes with the same security or function in server retrieval efficiency.

Key words: symmetric searchable encryption, multi-keyword ranked search, dynamic update, semantic extension

摘要： 针对云存储环境下已有的动态多关键词密文排序检索方案不支持关键词语义扩展、不具备前向安全和后向安全的问题，提出一种支持语义检索且具备前向安全和后向安全的动态多关键词密文排序检索方案。该方案通过构建语义关系图实现查询关键词的语义扩展；使用树索引结构实现数据的检索和动态更新；利用向量空间模型实现多关键词排序搜索；基于安全K近邻算法对维度扩展后的索引和查询向量进行加密。安全性分析表明，该方案在已知密文模型下是安全的且具有动态更新时的前向安全和后向安全。效率分析及仿真实验结果表明，该方案在服务器检索效率方面优于目前同类型具有相同安全性或相同功能的方案。

关键词: 对称可搜索加密, 多关键词排序检索, 动态更新, 语义扩展