6、TWith the rapid development of cloud storage, uploading local data to cloud storage pools becomes the first choice for data users. However, as cloud servers are not always trustworthy, it is often the case that before uploading, users would encrypt their
7、personal data first. To improve the efficiency in retrieving encrypted data, cryptography experts introduced the searchable encryption (SE) technology. Researches have shown that different SE secure index structures lead to different levels of keyword sea
8、rch efficiency –scientific index structures will substantially improve the efficiency in retrieving encrypted data. This paper, in the context of the searchable symmetric encryption technology employed in cloud stor