Multi-user multi-keyword privacy preserving ranked based search over encrypted cloud data

Many users now a day's placing their personal and professional data on the public cloud. But the fact is after outsourcing, users loose the local possession of their large size of data. As the storage and computing requirements of users are increasing, every time data is getting transferred to the remote server in larger chunks, but it's not necessary that the server on which the data is outsourced, is trusted server. In this paper, two of the privacy preserving issues about accessing the cloud data has been identified i.e. acuteness of keywords sent in queries and the data fetched as a result of those queries. Both of them should to be hidden. To keep the privacy of documents, it should get encrypted before outsourcing to the cloud. Privacy of the documents has been achieved using symmetric key cryptography algorithm i.e. Twofish. To retrieve the documents of user interest, multi-keyword query has to be fired which will result in accessing the top k ranked documents. Hiding the query pattern will achieve the privacy preserving access to data. Indexing has been developed to build an index of keywords from documents. Index will store hashed values of keywords. This paper has analysed and implemented Lucene indexing algorithm. Ranking of the results has been developed so as to improve the search result correctness as well as to embellish the user searching experience.