Biochemical experiments, such as diagnostics must be precise and trusted, and provide quick time to results. This has been enabled by automated digital microfluidics; however, it also exposes these experiments to security threats. Previous work has shown that the critical challenge in securing digital microfluidic devices is the lack of sensing resources. The micro-electrode-dot-array (MEDA) is a next-generation digital microfluidic biochip platform that supports fine-grained control and real-time sensing of droplet movements. These capabilities permit continuous monitoring and checkpoint (CP)-based validation of assay execution on MEDA. This article presents a class of “shadow attacks” that abuse the timing slack in the assay execution. State-of-the-art CP-based validation techniques cannot expose the shadow operations. We overcome this limitation by introducing extra CPs in the assay execution at time instances when the assay is prone to shadow attacks. We achieve this by identifying the conditions that enable shadow attacks. We use these conditions to minimize the number of CPs required to guarantee the correctness of bioassay implementation. Our simulation results confirm the effectiveness and practicality of the defense.

中文翻译：

---

微电极点阵生物芯片的安全检查点

生化实验（例如诊断）必须精确且值得信赖，并能快速获得结果。这是由自动化数字微流体技术实现的；然而，它也将这些实验暴露在安全威胁之下。以前的工作表明，保护数字微流体设备的关键挑战是缺乏传感资源。微电极点阵列 (MEDA) 是下一代数字微流控生物芯片平台，支持细粒度控制和实时感测液滴运动。这些功能允许对 MEDA 上的检测执行进行持续监控和基于检查点 (CP) 的验证。本文介绍了一类“影子攻击”，它们在化验执行中滥用时序裕量。最先进的基于 CP 的验证技术无法暴露影子操作。我们通过在分析容易受到影子攻击的时间实例中在分析执行中引入额外的 CP 来克服这一限制。我们通过识别启用影子攻击的条件来实现这一点。我们使用这些条件来最大限度地减少保证生物测定实施正确性所需的 CP 数量。我们的模拟结果证实了防御的有效性和实用性。