基于可拆分倒排索引的可搜索加密方案

为快速检索云环境下的加密数据，提出了一种高效的适用于批量数据处理场合的可搜索加密方案。首先，由客户端创建两个倒排索引，分别是存储了文件-关键词映射的文件索引和用于存储关键词-文件映射的空的搜索索引；然后，将这两个索引提交给云服务器。搜索索引是在用户检索过程中由云端根据搜索凭证和文件索引逐渐更新建立的，记录了已被检索关键词的检索结果，该方法将搜索索引的构建时间有效分摊了到了每次检索过程中并节省了存储空间。索引采用基于key-value结构的集合存储方式，支持索引的同时合并和拆分，即在添加和删除文件时，由客户端根据要添加或删除的文件集生成对应的文件索引和搜索索引，然后服务器对索引进行合并和拆分，从而实现文件的快速批量添加和删除。测试结果表明，所提方案极大提高了文件更新的效率，适用于批量数据处理。通过泄露函数证明了该方案能满足自适应动态选择关键词攻击下的不可区分性安全标准。

Searchable encryption scheme based on splittable inverted index

For retrieving the encrypted data in cloud environment quickly， an efficient searchable encryption scheme for batch data processing scenarios was proposed. Firstly， two inverted indexes were built by the client， one file index was used to store the file-keyword mapping， another empty search index was used to store keyword-file mapping. Then， these two indexes were submitted to the cloud server. The search index_{was gradually updated and constructed according to the search tokens and file indexesduring the user’s search by the cloud， and the search results of the searched keywords were recorded by this search index. In this way， the search index construction time was shared to each retrieval process effectively and the storage space of search index was reduced. A set storage method based on key-value structure was adopted by the indexes， which supported the at-the-same-time merging and splitting of index， which means when adding and deleting files， the corresponding file index and search index were generated by the client according to the file set to be added or deleted， then the server merged or split the indexes， so that the files were able to be added and deleted in batch quickly. Testing results show that the proposed scheme greatly improves the updating efficiency of files and is suitable for batch data processing. Through leakage function， it is proved that the proposed scheme can meet the indistinguishability security standard against adaptive dynamic keyword selection attack.}