ShEF: Shielded Enclaves for Cloud FPGAs

TL;DR

ShEF introduces a secure, customizable trusted execution environment for cloud FPGAs that protects sensitive data against a strong threat model, enabling secure acceleration with minimal performance overhead.

Contribution

ShEF is a novel TEE for cloud FPGAs that operates independently of CPU TEEs, providing customizable security with minimal overhead.

Findings

Prototype implementation demonstrates practical feasibility.

Secure storage application shows performance benefits.

Customizable Shield adapts to different security needs.

Abstract

FPGAs are now used in public clouds to accelerate a wide range of applications, including many that operate on sensitive data such as financial and medical records. We present ShEF, a trusted execution environment (TEE) for cloud-based reconfigurable accelerators. ShEF is independent from CPU-based TEEs and allows secure execution under a threat model where the adversary can control all software running on the CPU connected to the FPGA, has physical access to the FPGA, and can compromise the FPGA interface logic of the cloud provider. ShEF provides a secure boot and remote attestation process that relies solely on existing FPGA mechanisms for root of trust. It also includes a Shield component that provides secure access to data while the accelerator is in use. The Shield is highly customizable and extensible, allowing users to craft a bespoke security solution that fits their accelerator's memory access patterns, bandwidth, and security requirements at minimum performance and area overheads. We describe a prototype implementation of ShEF for existing cloud FPGAs, map ShEF to a performant and secure storage application, and measure the performance benefits of customizable security using five additional accelerators.