arXiv subjects

Marton Bognar

Publications and source records attributed to Marton Bognar.

3 recordsLinked to original sources

arXiv2026

dfence: Fine-Grained Speculation Barriers for Efficient and Effective Hardware-Software Protection in the Spectre Era (Extended Version)

Speculative execution attacks such as Spectre-PHT and Spectre-STL remain a critical security concern in modern processors. While software-based mitigations like Speculative Load Hardening (SLH) offer effective protection against Spectre-PHT, they are limited in scope and require software-managed speculative masks, which can be error-prone and costly. Defenses against Spectre-STL, such as the Speculative Store Bypass Disable bit (SSBD), incur additional performance overhead and lack fine-grained control. In this work, we introduce dfence, a new CPU instruction that generalizes SLH to mitigate both Spectre-PHT and Spectre-STL with minimal hardware support. dfence enables developers to annotate sensitive registers, with the hardware ensuring that these values do not leak transiently. We implement dfence in the Proteus CPU and evaluate its security and performance, demonstrating less than 1% average performance overhead for our benchmarks. In addition, to support easy and secure adoption, we design a type system that statically verifies the correct placement of dfence instructions in code.

cs.CR↗

arXiv2025

Libra: Architectural Support For Principled, Secure And Efficient Balanced Execution On High-End Processors (Extended Version)

Control-flow leakage (CFL) attacks enable an attacker to expose control-flow decisions of a victim program via side-channel observations. Linearization (i.e., elimination) of secret-dependent control flow is the main countermeasure against these attacks, yet it comes at a non-negligible cost. Conversely, balancing secret-dependent branches often incurs a smaller overhead, but is notoriously insecure on high-end processors. Hence, linearization has been widely believed to be the only effective countermeasure against CFL attacks. In this paper, we challenge this belief and investigate an unexplored alternative: how to securely balance secret-dependent branches on higher-end processors? We propose Libra, a generic and principled hardware-software codesign to efficiently address CFL on high-end processors. We perform a systematic classification of hardware primitives leaking control flow from the literature, and provide guidelines to handle them with our design. Importantly, Libra enables secure control-flow balancing without the need to disable performance-critical hardware such as the instruction cache and the prefetcher. We formalize the semantics of Libra and propose a code transformation algorithm for securing programs, which we prove correct and secure. Finally, we implement and evaluate Libra on an out-of-order RISC-V processor, showing performance overhead on par with insecure balanced code, and outperforming state-of-the-art linearized code by 19.3%.

cs.CR↗

arXiv2023

ProSpeCT: Provably Secure Speculation for the Constant-Time Policy (Extended version)

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.

cs.CR↗