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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. 

In this paper, we present HYPERRACE, an LLVM-based tool for instrumenting SGX enclave programs to eradicate all side-channel threats due to Hyper-Threading. HYPERRACE creates a shadow thread for each enclave thread and asks the underlying untrusted operating system to schedule both threads on the same physical core whenever enclave code is invoked, so that Hyper-Threading side channels are closed completely. Without placing additional trust in the operating system’s CPU scheduler, HYPERRACE conducts a physical-core co-location test: it first constructs a communication channel between the threads using a shared variable inside the enclave and then measures the communication speed to verify that the communication indeed takes place in the shared L1 data cache—a strong indicator of physical-core co-location. The key novelty of the work is the measurement of communication speed without a trustworthy clock; instead, relative time measurements are taken via contrived data races on the shared variable. It is worth noting that the emphasis of HYPERRACE’s defense against Hyper-Threading side channels is because they are open research problems. In fact, HYPERRACE also detects the occurrence of exception- or interrupt-based side channels, the solutions of which have been studied by several prior works.