面向高效加密云数据排序搜索的类别分组索引方法

针对现有可搜索加密领域所遇到的加密密钥维度高、更新不灵活和搜索速度慢等问题，我们提出了一种新型类别分组索引方法——CGIM.新方法将数据分类后，按类提取关键词建立分组索引，并采用分组加密方式实现以若干低维加密密钥代替高维加密密钥以缩短索引和查询请求的加密时间.此外，分组索引方法的每个组向量对应不同的类别，这样不仅可以实现分类更新以改善更新文档的灵活性，而且能够在检索过程中生成针对性陷门，从而进一步提高搜索的速度和效率.理论和实验分析表明，该方法是可行且有效的.

CGIM: Classificatory Group Index Method for Efficient Ranked Search of Encrypted Cloud Data

In order to solve the problems such as high dimension of encrypted key,low degree of update flexibility and low search speed in the field of encrypted search,we propose a novel classificatory group index method-CGIM.The method extracts category keywords from classified data to create group index,and uses group encryption method to transform a high-dimensional secret key into several low-dimensional keys to reduce the encryption time of indexes and query requests.In addition,each group in the index is corresponding to different category.Thus,the method can not only achieve classification update to improve the flexibility of document update,but also can generate a targeted trapdoor in the retrieval process to improve the search speed and efficiency further.Through security analysis and performance test,we prove that the method is feasible and effective.