Compiler-Based Approach to Enhance BliMe Hardware Usability

Abstract

Outsourced computing has emerged as an efficient platform for data processing, but it has raised security concerns due to potential exposure of sensitive data through runtime and side-channel attacks. To address these concerns, the BliMe hardware extensions offer a hardware-enforced taint tracking policy to prevent secret-dependent data exposure. However, such strict policies can hinder software usability on BliMe hardware.

While existing solutions can transform software to make it constant-time and more compatible with BliMe policies, they are not fully compatible with BliMe hardware. To strengthen the usability of BliMe hardware, we propose a compiler-based tool to detect and transform policy violations, ensuring constant-time compliance with BliMe. Our tool employs static analysis for taint tracking and employs transformation techniques including array access expansion, control-flow linearization and branchless select. We have implemented the tool on LLVM-11 to automatically convert existing source code.

We then conducted experiments on WolfSSL and OISA to examine the accuracy of the analysis and the effect of the transformations. Our evaluation indicates that our tool can successfully transform multiple code patterns. However, we acknowledge that certain code patterns are challenging to transform. Therefore, we also discuss manual approaches and explore potential future work to expand the coverage of our automatic transformations.