Toward Secure Checkpointing for Micro-Electrode-Dot-Array Biochips

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.