Ghost Arbitration: Mitigating Interconnect Side-Channel Timing Attacks in GPU

Network-on-chip (NoC) is a critical shared resource in scalable multicore processors; however, it is well-known that shared resources can lead to side-channel attacks. In this work, we demonstrate how contention for on-chip bandwidth in GPUs can lead to fine-grain information leakage and enable side-channel attacks. As a case study, we demonstrate how RSA key bit information can be leaked on a real GPU. We also describe how interconnect characteristics from the side-channel or an interconnect-gram can be used to fingerprint kernels executing on the GPU. To defend against such fine-grain side-channel attack, we propose secure arbitration that prevents information leakage while minimizing performance impact during normal execution. In particular, we present a novel ghost arbitration that prevents interconnect contention from being leveraged to leak information by keeping track of “ghost” requests or requests when other nodes receive free arbitration to enable least-recently-used priority. However, if the attacker reverse engineers the arbitration, a naive implementation of ghost arbitration can still lead to information leakage. Thus, we propose a weighted ghost arbitration that exploits “malicious” communication patterns to prevent information leakage with minimal loss in performance. Compared to previously proposed arbitration that is secure (e.g., strict time-division multiplexing), ghost arbitration is able to improve performance by up to $4\times$ •