Abstract
Data security has become an important requirement for clients when dealing with clouds that may fail due to faults in the software or hardware, or attacks from malicious insiders. Hence, building a highly dependable and reliable cloud system has become a critical research problem. This paper presents BFT-MCDB (Byzantine Fault Tolerance Multi-Clouds Database), a practical model for building a system with Byzantine fault tolerance in a multi-cloud environment. The model relies on a novel approach that combines Byzantine Agreement protocols and Shamir's secret sharing approach to detect Byzantine failure in a multi-cloud computing environment as well as ensuring the security of the stored data within the cloud. Using qualitative analysis, we show that adopting the Byzantine Agreement protocols in the proposed BFT-MCDB model increases system reliability and enables gains in regard to the three security dimensions (data integrity, data confidentiality, and service availability). We also carry out experiments to determine the overheads of using the Agreement protocols.