Privacy Preserving Ranked Keyword Search over Encrypted Cloud Data

We present a scheme that discusses secure rank based keyword search over an encrypted cloud data. The data that has to be outsourced is encrypted using symmetric encryption algorithm for data confidentiality. The index file of the keyword set that has to be searched is outsourced to the local trusted server where the keyword set that is generated from the data files is also stored. This is done so that any untrusted server cannot learn about the data with the help of the index formed. The index is created with the help of Aho-Corasick multiple strings matching algorithm which matches the pre-defined set of keywords with information in the data files to index them and store relevant data in B+ trees. Whenever the user searches for a keyword, the request is sent to the local trusted server and the indexed data is referred. The files are listed based on the certain relevance criteria. User requests for the required files to the un-trusted server. The parameters required for ranking is got from the data stored while indexing. Based on the ranking, the files are retrieved from the un-trusted server and displayed to the user. The proposed system can be extended to support Boolean search and Fuzzy keyword search techniques.