With the approach of cloud computing, more and more information data are distributed to the public cloud for economic savings and ease of access. But, the encryption of privacy information is necessary to guarantee the security. Now a days efficient data utilization, and search over encrypted cloud data has been a great challenge. Solution of existing methods depends only on the keyword of submitted query and didn�t examine the semantics of keyword. Thus the search schemes are not intelligent and also omit some semantically related documents. To overcome this problem, we propose a semantic expansion based similar search solution over encrypted cloud data. The solution of this method will return not only the exactly matched files, but also the files including the terms semantically related to the query keyword. In this scheme, a corresponding file metadata is constructed for each file. After this, both the encrypted file metadata set and file collection are uploaded to the cloud server. With the help of metadata set file, the cloud server maintains the inverted index and create semantic relationship library (SRL) for the keywords set. After receiving a query request from user , this server firstly search out the keywords that are related to the query keyword according to SRL. After this, both the query keyword and the extensional words are used to retrieve the files to fulfill the user request. These files are returned in order according to the total relevance score. Our detailed security analysis shows that our method is privacy-preserving and secure than the previous searchable symmetric encryption (SSE) security definition. Experimental evaluation demonstrates the efficiency and effectives of the scheme
