Abstract: Encryption is used to secure data before it is sent to cloud storage. It is done by data owner in order to protect data from misuse. However, there are issues when the encrypted data needs to accessed or searched for. The traditional search operation is not suitable for searching encrypted cloud data. Many researchers contributed towards providing search mechanisms on encrypted and outsourced cloud data. Xia et al. focused on secure multi-keyword ranked search on the encrypted and outsourced data to public cloud. They supported search operations and data dynamics as well. In this paper we proposed a methodology for performing flexible multi-keyword based optimized search scheme for encrypted cloud storage with user revocation feature. Users who are no longer supported by the system are revoked in order to ensure that the system remains secure. A model is built in order to have dynamic queries possible. Towards this end TF/IDF measure is used for flexible search operations on outsourced cloud data. We built a prototype application that shows multi-keyword ranked search with user revocation feature. The results revealed that the proposed system is flexible, secure and supporting optimized search over encrypted cloud data.

Keywords: Cloud data storage, encrypted cloud data, outsourcing, searching on encrypted cloud data, user revocation.