With the advent of Cloud Computing technology, data and computation outsourcing to cloud providers has become a growing tendency among companies and organizations. Nevertheless, the most important barrier in outsourcing is preserving the security and confidentiality of data against possible abuse by cloud providers. One of the main scenarios in utilization of cloud-based services is database outsourcing. In the topic of "secure database outsourcing", confidentiality of user data is preserved by means of cryptographic techniques. Since performing queries on a database is contradictory with being strongly encrypted, encryption alone is not sufficient. Therefore, the main challenge in secure outsourcing of database is to have confidentiality and query support simultaneously. Many solutions have been proposed by the researchers of applied cryptography. According to literature, the most studied solution is using weak encryptions such as deterministic encryption and order-preserving encryption. Nevertheless, none of the previous solutions have reached an acceptable level of security. Most of the earlier proposed frameworks are vulnerable to inference attacks like frequency analysis. In inference attacks, the cloud provider tries to break the confidentiality of system by taking advantage of some statistical information derived from the encrypted database or queries. In this thesis, we propose a framework for secure database outsourcing to resist such attacks. We have used bitmap indices that are secret-shared among two clouds. For query processing, each cloud obtains a share of the query result using methods in Secure Multi-Party Computation (SMPC) and sends its share to a third cloud, which holds the encrypted database. Therefore, none of the clouds can get any information about the user data or frequency and order of values in the database. We assume that these three clouds do not collude with each other. Keywords: Secure Database Outsourcing, Bitmap Index, Secret-Sharing, Secure Multi-Party Computation, Cryptography, Cloud Computing
