BACKGROUND

Cloud services provide on-demand access to cost-efficient computing resources such as data storage and computing power. Often, cloud services are available over public networks and hosted by unknown service providers. As a result, data in the cloud may be at risk of theft from malicious users or unauthorized users (e.g., service providers, etc.) that may obtain information through side channels. For example, side channels can expose information about data files being stored, usage of the data files, usage of services, and the like. To ensure confidentiality of the data, encryption can be applied to the data prior to transferring it to the cloud. In this case, the cloud must operate on the encrypted data in order to maintain the confidentiality of the data.

Cryptographic techniques such as fully homomorphic encryption (FHE) enable arbitrary computations on the data that do not reveal any information about the data. Thus, the data may be protected from malicious or unauthorized users. However, computations on data that has been encrypted through FHE suffer high computational costs. For example, an application that is fully encrypted with homomorphic encryption can suffer from significant processing/computation delays. Therefore, while it is considered secure, the drawbacks of slow processing speed can outweigh the benefits of the security.

