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1. Building GPU TEEs using CPU Secure Enclaves with GEVisor

   https://doi.org/10.1145/3620678.3624659  

   Wu, Xiaolong; Tian, Dave Jing; Kim, Chung Hwan (October 2023, ACM)

   Trusted execution environments (TEEs) have been proposed to protect GPU computation for machine learning applications operating on sensitive data. However, existing GPU TEE solutions either require CPU and/or GPU hardware modification to realize TEEs for GPUs, which prevents current systems from adopting them, or rely on untrusted system software such as GPU device drivers. In this paper, we propose using CPU secure enclaves, e.g., Intel SGX, to build GPU TEEs without modifications to existing hardware. To tackle the fundamental limitations of these enclaves, such as no support for I/O operations, we design and develop GEVisor, a formally verified security reference monitor software to enable a trusted I/O path between enclaves and GPU without trusting the GPU device driver. GEVisor operates in the Virtual Machine Extension (VMX) root mode, monitors the host system software to prevent unauthorized access to the GPU code and data outside the enclave, and isolates the enclave GPU context from other contexts during GPU computation. We implement and evaluate GEVisor on a commodity machine with an Intel SGX CPU and an NVIDIA Pascal GPU. Our experimental results show that our approach maintains an average overhead of 13.1% for deep learning and 18% for GPU benchmarks compared to native GPU computation while providing GPU TEEs for existing CPU and GPU hardware. 

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2. Defeating Speculative-Execution Attacks on SGX with HyperRace

   https://doi.org/10.1109/DSC47296.2019.8937682  

   Chen, Guoxing; Li, Mengyuan; Zhang, Fengwei; Zhang, Yinqian (November 2019, IEEE Conference on Dependable and Secure Computing)

   Speculative-execution attacks, such as SgxSpectre, Foreshadow, and MDS attacks, leverage recently disclosed CPU hardware vulnerabilities and micro-architectural side channels to breach the confidentiality and integrity of Intel Software Guard eXtensions (SGX). Unlike traditional micro-architectural side-channel attacks, speculative-execution attacks extract any data in the enclave memory, which makes them very challenging to defeat purely from the software. However, to date, Intel has not completely mitigated the threats of speculative-execution attacks from the hardware. Hence, future attack variants may emerge. This paper proposes a software-based solution to speculative-execution attacks, even with the strong assumption that confidentiality of enclave memory is compromised. Our solution extends an existing work called HyperRace, which is a compiler-assisted tool for detecting Hyper-Threading based side-channel attacks against SGX enclaves, to thwart speculative-execution attacks from within SGX enclaves. It requires supports from the untrusted operating system, e.g., for temporarily disabling interrupts, but verifies the OS's behaviors. Additional microcode upgrades are required from Intel to secure the attestation flow. 

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3. Detecting Privileged Side-Channel Attacks in Shielded Execution with Déjà Vu

   https://doi.org/10.1145/3052973.3053007  

   Chen, Sanchuan; Zhang, Xiaokuan; Reiter, Michael K.; Zhang, Yinqian (April 2017, ACM Asia Conference on Computer & Communications Security 2017)

   Intel Software Guard Extension (SGX) protects the confidentiality and integrity of an unprivileged program running inside a secure enclave from a privileged attacker who has full control of the entire operating system (OS). Program execution inside this enclave is therefore referred to as shielded. Unfortunately, shielded execution does not protect programs from side-channel attacks by a privileged attacker. For instance, it has been shown that by changing page table entries of memory pages used by shielded execution, a malicious OS kernel could observe memory page accesses from the execution and hence infer a wide range of sensitive information about it. In fact, this page-fault side channel is only an instance of a category of side-channel attacks, here called privileged side-channel attacks, in which privileged attackers frequently preempt the shielded execution to obtain fine-grained side-channel observations. In this paper, we present Déjà Vu, a software framework that enables a shielded execution to detect such privileged side-channel attacks. Specifically, we build into shielded execution the ability to check program execution time at the granularity of paths in its control-flow graph. To provide a trustworthy source of time measurement, Déjà Vu implements a novel software reference clock that is protected by Intel Transactional Synchronization Extensions (TSX), a hardware implementation of transactional memory. Evaluations show that Déjà Vu effectively detects side-channel attacks against shielded execution and against the reference clock itself. 

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4. A Comparison Study of Intel SGX and AMD Memory Encryption Technology

   Mofrad, Saeid; Zhang, Fengwei (July 2018, The Hardware and Architectural Support for Security and Privacy(HASP'18), in conjunction with The 45th International Symposium on Computer Architecture (ISCA'18))

   Hardware-assisted trusted execution environments are secure isolation technologies that have been engineered to serve as efficient defense mechanisms to provide a security boundary at the system level. Hardware vendors have introduced a variety of hardware-assisted trusted execution environments including ARM TrustZone, Intel Management Engine, and AMD Platform Security Processor. Recently, Intel Software Guard eXtensions (SGX) and AMD Memory Encryption Technology have been introduced. To the best of our knowledge, this paper presents the first comparison study between Intel SGX and AMD Memory Encryption Technology in terms of functionality, use scenarios, security, and performance implications. We summarize the pros and cons of these two approaches in comparison to each other. 

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5. A comparison study of intel SGX and AMD memory encryption technology

   https://doi.org/10.1145/3214292.3214301  

   Mofrad, Saeid; Zhang, Fengwei; Lu, Shiyong; Shi, Weidong (January 2018, 7th International Workshop on Hardware and Architectural Support for Security and Privacy)

   Hardware-assisted trusted execution environments are secure isolation technologies that have been engineered to serve as efficient defense mechanisms to provide a security boundary at the system level. Hardware vendors have introduced a variety of hardware-assisted trusted execution environments including ARM TrustZone, Intel Management Engine, and AMD Platform Security Processor. Recently, Intel Software Guard eXtensions (SGX) and AMD Memory Encryption Technology have been introduced. To the best of our knowledge, this paper presents the first comparison study between Intel SGX and AMD Memory Encryption Technology in terms of functionality, use scenarios, security, and performance implications. We summarize the pros and cons of these two approaches in comparison to each other. 

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