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As an emerging lab-on-a-chip technology platform, digital microfluidic biochips (DMFBs) have been widely used for executing various laboratory procedures in biochemistry and biomedicine such as gene sequencing and near-patient diagnosis, with the advantages of low reagent consumption, high precision, and miniaturization and integration. With the ongoing rapid deployment of DMFBs, however, these devices are now facing serious and complicated security challenges that not only damage their functional integrity but also affect their system reliability. In this article, we present a systematic review of DMFB security, focusing on both the state-of-the-art attack and defense techniques. First, the overall security situation, the working principle, and the corresponding fabrication technology of DMFBs are introduced. Afterwards, existing attack approaches are divided into several categories and discussed in detail, including denial of service, intellectual property piracy, bioassay tampering, layout modification, actuation sequence tampering, concentration altering, parameter modification, reading forgery, and information leakage. To prevent biochips from being damaged by these attack behaviors, a number of defense measures have been proposed in recent years. Accordingly, we further classify these techniques into three categories according to their respective defense purposes, including confidentiality protection, integrity protection, and availability protection. These measures, to varying degrees, can provide effective protection for DMFBs. Finally, key trends and directions for future research that are related to the security of DMFBs are discussed from several aspects, e.g., manufacturing materials, biochip structure, and usage environment, thus providing new ideas for future biochip protection.

As the next generation of digital microfluidic biochips (DMFBs) platform, Micro-electrode-dot-array (MEDA) has sea-of-micro-electrodes that support fine-grained control of the droplet and constant real-time monitoring of droplet paths. As MEDA biochips are expected to be had a booming market in the near future, their security, especially the protection of intellectual property (IP), has become the focus of the academic community. In this paper, we first propose a logic encryption-based IP protection scheme for MEDA biochips, called MEDASec, which is without modifying the structure. Our scheme aims to hide the droplet mix-split operation in bioassay, making the IP akin to a black-box in the manufacturing process. Besides, increasing computing power has facilitated the threat of brute force attacks on the secret key. In response to the brute force attack, we propose security metrics for the first time, called RRA, to evaluate the ratio of reagents that result from biochemical reactions. Experimental results on multiple bioassays demonstrate the effectiveness of the proposed logical encryption strategy against the brute force attack.

The digital microfluidic biochips (DMFBs) have the advantages of high precision, small consumption of samples/reagents, and high flexibility in experimental places. Nowadays, DMFB technology has been implemented in industry, such as by illumina. However, similar to the situation faced in integrated circuits, DMFBs also suffer from various security risks and end users usually know little about these security threats. Accordingly, in this paper, we propose a survey on DMFBs security in the research community. First, we prevent an overview of the attack behaviors in DMFBs and list them according to the design and manufacture flow. Then, we outline the current defense techniques and classify them into several categories according to their corresponding purposes and functions. Finally, the comparison between security threats faced in DMFBs and the corresponding defense techniques are provided and analyzed in detail, thus presenting the future research trends in DMFBs security.