Preserving Multi-relational Outsourced Databases Confidentiality using Fragmentation and Encryption

Confidentiality and privacy of outsourced data has become one of the pressing challenges in Cloud computing. Outsourced data often includes sensitive personally identifiable information. When data is outsourced, sensitive information will not be under the control of its owners, but under the control of an external service provider. In this paper, we define an approach allowing the protection of confidentiality of sensitive information in outsourced multi-relational databases by improving an existing approach based on a combination of fragmentation and encryption. Then we define a secure and effective technique for querying data hosted on several service providers. Finally, we improve the security of the querying technique in order to protect data confidentiality under a collaborative Cloud storage service providers model.