arXiv subjects

Tian

Publications and source records attributed to Tian.

4 recordsLinked to original sources

arXiv2025

SoK: Kicking CAN Down the Road. Systematizing CAN Security Knowledge

For decades, the Controller Area Network (CAN) has served as the primary in-vehicle bus (IVB) and extended its use to many non-vehicular systems. Over the past years, CAN security has been intensively scrutinized, yielding extensive research literature. Despite its wealth, the literature lacks structured systematization, complicating efforts to assess attack severity, defense efficacy, identify security gaps, or root causes. This leaves non experts uncertain about the relevancy of specific attacks or defenses to their systems, inadvertently portraying CAN as irredeemably insecure. Further, the introduction of new IVB technologies--CAN evolutions, add-ons, and alternative buses--with heightened security claims risks fostering the misconception that merely adopting these technologies resolves CAN's security challenges. This paper systematizes existing CAN security knowledge, presenting a comprehensive taxonomy and assessment models of attackers, attacks, and defenses. It identifies replicable attacks and defense gaps, investigating their root causes as inherent, accidental, unique, or universal. It then extrapolates these insights to emerging IVB technologies by formally analyzing three emerging IVBs to identify shared root causes with CAN and assess their ability to close security gaps. The findings challenge common perceptions, demonstrating that CAN is more securable than perceived, that most insecurity root causes are shared across IVBs, and that merely adopting newer IVB technology does not solve persistent security issues. The paper concludes by highlighting future research directions to secure IVB communication down the road.

cs.CR↗

arXiv2025

Thunderhammer: Rowhammer Bitflips via PCIe and Thunderbolt (USB-C)

In recent years, Rowhammer has attracted significant attention from academia and industry alike. This technique, first published in 2014, flips bits in memory by repeatedly accessing neighbouring memory locations. Since its discovery, researchers have developed a substantial body of work exploiting Rowhammer and proposing countermeasures. These works demonstrate that Rowhammer can be mounted not only through native code, but also via remote code execution, such as JavaScript in browsers, and over networks. In this work, we uncover a previously unexplored Rowhammer vector. We present Thunderhammer, an attack that induces DRAM bitflips from malicious peripherals connected via PCIe or Thunderbolt (which tunnels PCIe). On modern DDR4 systems, we observe that triggering bitflips through PCIe requests requires precisely timed access patterns tailored to the target system. We design a custom device to reverse engineer critical architectural parameters that shape PCIe request scheduling, and to execute effective hammering access patterns. Leveraging this knowledge, we successfully demonstrate Rowhammer-induced bitflips in DDR4 memory modules via both PCIe slot connections and Thunderbolt ports tunnelling PCIe.

cs.CR↗

arXiv2025

D-LiFT: Improving LLM-based Decompiler Backend via Code Quality-driven Fine-tuning

As one of the key tools in many security tasks, decompilers reconstruct human-readable source code from binaries. Yet, despite recent advances, their outputs often suffer from syntactic and semantic errors and remain difficult to read. Recently, with the advent of large language models (LLMs), researchers began to explore the potential of LLMs to refine decompiler output. Nevertheless, our study of these approaches reveals their problems, such as introducing new errors and relying on unreliable accuracy validation. In this paper, we present D-LIFT, an enhanced decompiler-LLM pipeline with a fine-tuned LLM using code quality-aware reinforcement learning. Unlike prior work that overlooks preserving accuracy, D-LIFT adheres to a key principle for enhancing the quality of decompiled code: preserving accuracy while improving readability. Central to D-LIFT, we propose D-Score, an integrated code quality assessment system to score the decompiled source code from multiple aspects, and use it to guide reinforcement learning fine-tuning and to select the best output during inference. In line with our principle, D-Score assigns low scores to any inaccurate output and only awards higher scores for readability to code that passes the accuracy check. Our implementation, based on Ghidra and a range of LLMs, demonstrates significant improvements for the accurate decompiled code from the coreutils and util-linux projects. Compared to baseline LLMs without D-Score-driven fine-tuning, our trained LLMs produce 55.3% more improved decompiled functions, as measured by D-Score. Overall, D-LIFT improves the quality of 68.2% of all the functions produced by the native decompiler.

cs.CR↗

arXiv2024

Apodized Slanted Grating Couplers for LiDAR Applications

Solid state LiDAR systems traditionally rely on costly active components for efficient beam scanning. In this study, we propose a cost-effective, purely passive steering approach using apodized slanted grating couplers. Through apodization, we achieve a uniform upward emission profile and enhanced upward transmission. Theoretical calculations indicate successful steering of 91.5$^\circ$x42.8$^\circ$. Experimental results closely match theoretical predictions, validating the capabilities of our passive steering concept. Additionally, the grating couplers, with a length of 3mm, enable a farfield FWHM of 0.026$^\circ$, further enhancing sensing resolution.

physics.optics↗