Achieving trustworthy homomorphic encryption by combining it with a trusted execution environment

Cloud database services become very appealing solutions. They offer performance and storage capabilities that client platforms do not have. However, in order to protect the users’ confidentiality and to ensure the integrity of their computations, solutions often use one of three approaches: a) Encrypting the data prior to uploading it with some symmetric encryption; b) Using a Trusted Execution Environments (TEE) such as OS containers, Virtual Machines or Intel’s Software Guard Extension (SGX); c) using Homomorphic Encryption (HE) schemes. A newer approach, which we call the”combined model” uses a TEE to guarantee the integrity and correctness of the database code and data, while the data itself is encrypted with some HE scheme. In this paper, we explain the combined model and we show how to use it in the context of modern Multi Party Computations (MPC) schemes. In addition, we demonstrate how to construct a voting system that leverages its capabilities.