A Practical Remote Power Attack on Machine Learning Accelerators in Cloud FPGAs

The security and performance of FPGA-based accelerators play vital roles in today's cloud services. In addition to supporting convenient access to high-end FPGAs, cloud vendors and third-party developers now provide numerous FPGA accelerators for machine learning models. However, the security of accelerators developed for state-of-the-art Cloud FPGA environments has not been fully explored, since most remote accelerator attacks have been prototyped on local FPGA boards in lab settings, rather than in Cloud FPGA environments. To address existing research gaps, this work analyzes three existing machine learning accelerators developed in Xilinx Vitis to assess the potential threats of power attacks on accelerators in Amazon Web Services (AWS) F1 Cloud FPGA platforms, in a multi-tenant setting. The experiments show that malicious co-tenants in a multi-tenant environment can instantiate voltage sensing circuits as register-transfer level (RTL) kernels within the Vitis design environment to spy on co-tenant modules. A methodology for launching a practical remote power attack on Cloud FPGAs is also presented, which uses an enhanced time-to-digital (TDC) based voltage sensor and auto-triggered mechanism. The TDC is used to capture power signatures, which are then used to identify power consumption spikes and observe activity patterns involving the FPGA shell, DRAM on the FPGA board, or the other co-tenant victim's accelerators. Voltage change patterns related to shell use and accelerators are then used to create an auto-triggered attack that can automatically detect when to capture voltage traces without the need for a hard-wired synchronization signal between victim and attacker. To address the novel threats presented in this work, this paper also discusses defenses that could be leveraged to secure multi-tenant Cloud FPGAs from power-based attacks.