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FPGA virtualization has garnered significant industry and academic interests as it aims to enable multi-tenant cloud systems that can accommodate multiple users' circuits on a single FPGA. Although this approach greatly enhances the efficiency of hardware resource utilization, it also introduces new security concerns. As a representative study, one state-of-the-art (SOTA) adversarial fault injection attack, named Deep-Dup, exemplifies the vulnerabilities of off-chip data communication within the multi-tenant cloud-FPGA system. Deep-Dup attacks successfully demonstrate the complete failure of a wide range of Deep Neural Networks (DNNs) in a black-box setup, by only injecting fault to extremely small amounts of sensitive weight data transmissions, which are identified through a powerful differential evolution searching algorithm. Such emerging adversarial fault injection attack reveals the urgency of effective defense methodology to protect DNN applications on the multi-tenant cloud-FPGA system. This paper, for the first time, presents a novel moving-target-defense (MTD) oriented defense framework DeepShuffle, which could effectively protect DNNs on multi-tenant cloud-FPGA against the SOTA Deep-Dup attack, through a novel lightweight model parameter shuffling methodology. DeepShuffle effectively counters the Deep-Dup attack by altering the weight transmission sequence, which effectively prevents adversaries from identifying security-critical model parameters from the repeatability of weight transmission during each inference round. Importantly, DeepShuffle represents a training-free DNN defense methodology, which makes constructive use of the typologies of DNN architectures to achieve being lightweight. Moreover, the deployment of DeepShuffle neither requires any hardware modification nor suffers from any performance degradation. We evaluate DeepShuffle on the SOTA open-source FPGA-DNN accelerator, Vertical Tensor Accelerator (VTA), which represents the practice of real-world FPGA-DNN system developers. We then evaluate the performance overhead of DeepShuffle and find it only consumes an additional ~3% of the inference time compared to the unprotected baseline. DeepShuffle improves the robustness of various SOTA DNN architectures like VGG, ResNet, etc. against Deep-Dup by orders. It effectively reduces the efficacy of evolution searching-based adversarial fault injection attack close to random fault injection attack, e.g., on VGG-11, even after increasing the attacker's effort by 2.3x, our defense shows a ~93% improvement in accuracy, compared to the unprotected baseline. 

Architecture reverse engineering has become an emerging attack against deep neural network (DNN) implemen- tations. Several prior works have utilized side-channel leakage to recover the model architecture while the an DNN is executing on a hardware acceleration platform. In this work, we target an open- source deep-learning accelerator, Versatile Tensor Accelerator (VTA), and utilize electromagnetic (EM) side-channel leakage to comprehensively learn the association between DNN architecture configurations and EM emanations. We also consider the holistic system – including the low-level tensor program code of the VTA accelerator on a Xilinx FPGA, and explore the effect of such low- level configurations on the EM leakage. Our study demonstrates that both the optimization and configuration of tensor programs will affect the EM side-channel leakage. Gaining knowledge of the association between low-level tensor program and the EM emanations, we propose NNReArch, a lightweight tensor program scheduling framework against side- channel-based DNN model architecture reverse engineering. Specifically, NNReArch targets reshaping the EM traces of different DNN operators, through scheduling the tensor program execution of the DNN model so as to confuse the adversary. NNReArch is a comprehensive protection framework supporting two modes, a balanced mode that strikes a balance between the DNN model confidentiality and execution performance, and a secure mode where the most secure setting is chosen. We imple- ment and evaluate the proposed framework on the open-source VTA with state-of-the-art DNN architectures. The experimental results demonstrate that NNReArch can efficiently enhance the model architecture security with a small performance overhead. In addition, the proposed obfuscation technique makes reverse engineering of the DNN architecture significantly harder. 

The wide deployment of Deep Neural Networks (DNN) in high-performance cloud computing platforms brought to light multi-tenant cloud field-programmable gate arrays (FPGA) as a popular choice of accelerator to boost performance due to its hardware reprogramming flexibility. Such a multi-tenant FPGA setup for DNN acceleration potentially exposes DNN interference tasks under severe threat from malicious users. This work, to the best of our knowledge, is the first to explore DNN model vulnerabilities in multi-tenant FPGAs. We propose a novel adversarial attack framework: Deep-Dup, in which the adversarial tenant can inject adversarial faults to the DNN model in the victim tenant of FPGA. Specifically, she can aggressively overload the shared power distribution system of FPGA with malicious power-plundering circuits, achieving adversarial weight duplication (AWD) hardware attack that duplicates certain DNN weight packages during data transmission between off-chip memory and on-chip buffer, to hijack the DNN function of the victim tenant. Further, to identify the most vulnerable DNN weight packages for a given malicious objective, we propose a generic vulnerable weight package searching algorithm, called Progressive Differential Evolution Search (P-DES), which is, for the first time, adaptive to both deep learning white-box and black-box attack models. The proposed Deep-Dup is experimentally validated in a developed multi-tenant FPGA prototype, for two popular deep learning applications, i.e., Object Detection and Image Classification. Successful attacks are demonstrated in six popular DNN architectures (e.g., YOLOv2, ResNet-50, MobileNet, etc.) on three datasets (COCO, CIFAR-10, and ImageNet).