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1. OPERA: Open Remote Attestation for Intel's Secure Enclaves

   https://doi.org/10.1145/3319535.3354220  

   Chen, Guoxing; Zhang, Yinqian; Lai, Ten-Hwang (January 2019, ACM Conference on Computer and Communications Security)

   Intel Software Guard Extensions (SGX) remote attestation enables enclaves to authenticate hardware inside which they run, and attest the integrity of their enclave memory to the remote party. To enforce direct control of attestation, Intel mandates attestation to be verified by Intel’s attestation service. This Intel-centric attestation model, however, neither protects privacy nor performs efficiently when distributed and frequent attestation is required. This paper presents OPERA, an Open Platform for Enclave Remote Attestation. Without involving Intel’s attestation service while conducting attestation, OPERA is unchained from Intel, although it relies on Intel to establish a chain of trust whose anchor point is the secret rooted in SGX hardware. OPERA is open, as the implementation of its attestation service is completely open, allowing any enclave developer to run her own OPERA service, and its execution is publicly verifiable and hence trustworthy; OPERA is privacy-preserving, as the attestation service does not learn which enclave is being attested or when the attestation takes place; OPERA is performant, as it does not rely on a single-point-of-verification and also reduces the latency of verification. 

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2. On the Root of Trust Identification Problem

   https://doi.org/10.1145/3412382.3458274  

   De Oliveira Nunes, Ivan; Ding, Xuhua; Tsudik, Gene (May 2021, IPSN '21: Proceedings of the 20th International Conference on Information Processing in Sensor Networks (co-located with CPS-IoT Week 2021))

   null (Ed.)

   Trusted Execution Environments (TEEs) are becoming ubiquitous and are currently used in many security applications: from personal IoT gadgets to banking and databases. Prominent examples of such architectures are Intel SGX, ARM TrustZone, and Trusted Platform Modules (TPMs). A typical TEE relies on a dynamic Root of Trust (RoT) to provide security services such as code/data confidentiality and integrity, isolated secure software execution, remote attestation, and sensor auditing. Despite their usefulness, there is currently no secure means to determine whether a given security service or task is being performed by the particular RoT within a specific physical device. We refer to this as the Root of Trust Identification (RTI) problem and discuss how it inhibits security for applications such as sensing and actuation. We formalize the RTI problem and argue that security of RTI protocols is especially challenging due to local adversaries, cuckoo adversaries, and the combination thereof. To cope with this problem we propose a simple and effective protocol based on biometrics. Unlike biometric-based user authentication, our approach is not concerned with verifying user identity, and requires neither pre-enrollment nor persistent storage for biometric templates. Instead, it takes advantage of the difficulty of cloning a biometric in real-time to securely identify the RoT of a given physical device, by using the biometric as a challenge. Security of the proposed protocol is analyzed in the combined Local and Cuckoo adversarial model. Also, a prototype implementation is used to demonstrate the protocol’s feasibility and practicality. We further propose a Proxy RTI protocol, wherein a previously identified RoT assists a remote verifier in identifying new RoTs. 

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3. Challenges For Scaling Applications Across Enclaves

   https://doi.org/10.1145/3152701.3152710  

   Beekman, Jethro G.; Porter, Donald E. (October 2017, Proceedings of the 2nd Workshop on System Software for Trusted Execution)

   At Fortanix, we are developing cloud-scale security infras- tructure using SGX. For example, our Self-Defending Key Management Service (SDKMS) can span multiple machines and enclaves, rendering a more scalable and cost-effective alternative to a traditional Hardware Security Module (HSM). This paper describes several subtle, practical, and under- explored problems in the space of building scalable, trusted applications, based on our experience building distributed SGX systems. In particular, we discuss shortcomings in re- mote attestation for microservice-style applications, soft- ware updates, and opportunities to reflect trustworthy development practices in attestation features. 

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4. Trusted IP Solution in Multi-tenant Cloud FPGA Platform

   https://doi.org/10.1109/WF-IoT54382.2022.10152167  

   Ahmed, Muhammed Kawser; Saha, Sujan Kumar; Bobda, Christophe (October 2022, 2022 IEEE 8th World Forum on Internet of Things (WF-IoT))

   Because FPGAs outperform traditional processing cores like CPUs and GPUs in terms of performance per watt and flexibility, they are being used more and more in cloud and data center applications. There are growing worries about the security risks posed by multi-tenant sharing as the demand for hardware acceleration increases and gradually gives way to FPGA multi-tenancy in the cloud. The confidentiality, integrity, and availability of FPGA-accelerated applications may be compromised if space-shared FPGAs are made available to many cloud tenants. We propose a root of trust-based trusted execution mechanism called TrustToken to prevent harmful software-level attackers from getting unauthorized access and jeopardizing security. With safe key creation and truly random sources, TrustToken creates a security block that serves as the foundation of trust-based IP security. By offering crucial security characteristics, such as secure, isolated execution and trusted user interaction, TrustToken only permits trustworthy connection between the non-trusted third-party IP and the rest of the SoC environment. The suggested approach does this by connecting the third-party IP interface to the TrustToken Controller and running run-time checks on the correctness of the IP authorization(Token) signals. With an emphasis on software-based assaults targeting unauthorized access and information leakage, we offer a noble hardware/software architecture for trusted execution in FPGA-accelerated clouds and data centers. 

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5. CASU: Compromise Avoidance via Secure Update for Low-End Embedded Systems

   https://doi.org/10.1145/3508352.3549450  

   De Oliveira Nunes, Ivan; Jakkamsetti, Sashidhar; Kim, Youngil; Tsudik, Gene (October 2022, ICCAD '22: Proceedings of the 41st IEEE/ACM International Conference on Computer-Aided Design)

   Guaranteeing runtime integrity of embedded system software is an open problem. Trade-offs between security and other priorities (e.g., cost or performance) are inherent, and resolving them is both challenging and important. The proliferation of runtime attacks that introduce malicious code (e.g., by injection) into embedded devices has prompted a range of mitigation techniques. One popular approach is Remote Attestation (RA), whereby a trusted entity (verifier) checks the current software state of an untrusted remote device (prover). RA yields a timely authenticated snapshot of prover state that verifier uses to decide whether an attack occurred. Current RA schemes require verifier to explicitly initiate RA, based on some unclear criteria. Thus, in case of prover's compromise, verifier only learns about it late, upon the next RA instance. While sufficient for compromise detection, some applications would benefit from a more proactive, prevention-based approach. To this end, we construct CASU: Compromise Avoidance via Secure Updates. CASU is an inexpensive hardware/software co-design enforcing: (i) runtime software immutability, thus precluding any illegal software modification, and (ii) authenticated updates as the sole means of modifying software. In CASU, a successful RA instance serves as a proof of successful update, and continuous subsequent software integrity is implicit, due to the runtime immutability guarantee. This obviates the need for RA in between software updates and leads to unobtrusive integrity assurance with guarantees akin to those of prior RA techniques, with better overall performance. 

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