HAO enables stable reinforcement learning under FHE encryption by preventing polynomial approximation errors from accumulating—achieving 0% boundary violations versus 83.8% for unprotected baselines, making privacy-preserving RL practically viable.
This paper solves a critical problem in privacy-preserving reinforcement learning: when you encrypt data with Fully Homomorphic Encryption (FHE) for cloud computation, you must replace nonlinear operations with polynomial approximations, which causes training to diverge.