Formal Processor Model Providing Provably Secure Speculation For The Constant-Time Policy


A new technical paper titled “ProSpeCT: Provably Secure Speculation for the Constant-Time Policy” was published by researchers at imec-DistriNet, KU Leuven, CEA, and INRIA. This paper was included at the recent 32nd USENIX Security Symposium.

“We propose ProSpeCT, a generic formal processor model providing provably secure speculation for the constant-time policy. For constant-time programs under a non-speculative semantics, ProSpeCT guarantees that speculative and out-of-order execution cause no microarchitectural leaks. This guarantee is achieved by tracking secrets in the processor pipeline and ensuring that they do not influence the microarchitectural state during speculative execution. Our formalization covers a broad class of speculation mechanisms, generalizing prior work. As a result, our security proof covers all known Spectre attacks, including load value injection (LVI) attacks.

In addition to the formal model, we provide a prototype hardware implementation of ProSpeCT on a RISC-V processor and show evidence of its low impact on hardware cost, performance, and required software changes. In particular, the experimental evaluation confirms our expectation that for a compliant constant-time binary, enabling ProSpeCT incurs no performance overhead.”

Find the technical paper here. August 2023.

Daniel, Lesly-Ann, Marton Bognar, Job Noorman, Sébastien Bardin, Tamara Rezk, and Frank Piessens. “ProSpeCT: Provably Secure Speculation for the Constant-Time Policy.” In 32nd USENIX Security Symposium (USENIX Security 23). 2023.

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