CIBPU: A Conflict-Invisible Secure Branch Prediction Unit

This paper presents CIBPU, a new secure branch prediction unit (BPU, a component that helps processors predict which instructions to execute next) that protects against attacks trying to infer sensitive information by observing how the BPU behaves. Unlike previous designs that either isolated the BPU physically or used encryption with frequent key updates, CIBPU uses redundant storage (extra copies of data), smart indexing, and encryption without periodic key changes to hide branch conflicts (situations where different instructions compete for the same storage space) from attackers. The researchers tested CIBPU in simulators and on real hardware, finding it adds only about 2-4% performance slowdown, which is better than other secure branch prediction approaches.