Enforcing Correct Behavior without Trust in Cloud Key-Value Databases

Traditional computation outsourcing and modern cloud computing are affected by a common risk of distrust between service requestor and service provider. We propose a novel protocol, named Probus, that offers guarantees of correct behavior to both parts without assuming any trust relationship between them in the context of cloud-based key-value databases. Probus allows a service requestor to have evidence of cloud provider misbehavior on its data, and a cloud provider to defend itself from false accusations by demonstrating the correctness of its operations. Accusation and defense proofs are based on cryptographic mechanisms that can be verified by a third party. Probus improves the state-of-the-art by introducing novel solutions that allow for efficient verification of data security properties and by limiting the overhead required to provide its security guarantees. Thanks to Probus it is possible to check the correctness of all the results generated by a cloud service, thus improving weaker integrity assurance based on probabilistic verifications that are adopted by related work.