The computer systems security arms race between attackers and defenders are largely taken place in the domain of software systems, but as hardware complexity and design processes have envolved, novel and potent hardware-based security threats are now possible. This article presents Unused Circuit Identification (UCI), an approach for detecting suspicious circuits during design time, and BlueChip, a hybrid hardware/software approach to detaching suspicious circuits and making up for UCI classifier errors during runtime.

Overcoming an untrusted computing base: detecting and removing malicious hardware automatically

Severe security threats and alerts associated with the use of smart devices have drawn increasing public attentions since the inception of Internet of Things (IoT) in late 1990s. IoT devices pose a unique and challenging scenario for hardware security because of their ubiquity and area-power cost constraints. Traditional software techniques and established cryptographic methods are either inadequate or impractical due to the computational capacity and permanent storage required to process and maintain the privacy of the secret key. In this light, Physical Unclonable Function (PUF), a burgeoning technology rooted in 2002, comes in handy as an inexpensive and yet effective security primitive to overcome the forgery tagging problem by its radically different way of generating and processing secret keys in security hardware. PUFs are hardware structures or functions designed to utilize the physical disorder of random nanoscale phenomena for the derivation of keys without having to keep any security-critical information explicitly in hardware. As we usher PUF into its 15th anniversary in 2017, it is timely to review the advancements of PUF over the past decade. Specifically, this survey addresses three fundamental questions which are at all times relevant in the security arms race. These questions are: how secure can a PUF be? what differences have PUFs brought to security applications and how do these differences impact existing security protocols? how is hardware implementation research influenced by the opportunities of nanotechnologies and new discoveries of disorder-based physical phenomena? It is hoped that this retrospective study of problems and solutions encountered in the journey of developing PUF to its current state will foreshadow the challenges and opportunities for future sustainable activities in the field.

A Retrospective and a Look Forward: Fifteen Years of Physical Unclonable Function Advancement

We have developed pneumatic logic circuits and microprocessors built with microfluidic channels and valves in polydimethylsiloxane (PDMS). The pneumatic logic circuits perform various combinational and sequential logic calculations with binary pneumatic signals (atmosphere and vacuum), producing cascadable outputs based on Boolean operations. A complex microprocessor is constructed from combinations of various logic circuits and receives pneumatically encoded serial commands at a single input line. The device then decodes the temporal command sequence by spatial parallelization, computes necessary logic calculations between parallelized command bits, stores command information for signal transportation and maintenance, and finally executes the command for the target devices. Thus, such pneumatic microprocessors will function as a universal on-chip control platform to perform complex parallel operations for large-scale integrated microfluidic devices. To demonstrate the working principles, we have built 2-bit, 3-bit, 4-bit, and 8-bit microprocessors to control various target devices for applications such as four color dye mixing, and multiplexed channel fluidic control. By significantly reducing the need for external controllers, the digital pneumatic microprocessor can be used as a universal on-chip platform to autonomously manipulate microfluids in a high throughput manner.

Microfluidic pneumatic logic circuits and digital pneumatic microprocessors

Digital microfluidic biochips (DMFBs) integrated with processors and arrays of sensors form cyberphysical systems and consequently face a variety of unique, recently described security threats. It has been noted that techniques used for error recovery can provide some assurance of integrity when a cyberphysical DMFB is under attack. This paper proposes the use of such hardware for security purposes through the randomization of checkpoints in both space and time, and provides design guidelines for designers of such systems. We define security metrics and present techniques for improving performance through static checkpoint maps, and describe performance tradeoffs associated with static and random checkpoints. We also provide detailed classification of attack models and demonstrate the feasibility of our techniques with case studies on assays implemented in typical DMFB hardware.

Secure Randomized Checkpointing for Digital Microfluidic Biochips

Wireless sensors are increasingly penetrating every domain of our lives through integration with Internet of Things, eg, such devices are widely incorporated into smart buildings and for monitoring critical industrial infrastructure Sensing, collecting and communication of sensor data, however, are under threat from various attacks due to the difficulty in implementing proper protection mechanisms and limited computational resources available in these cost-sensitive devices This paper expands on recent research on physical unclonable function (PUF) sensors to secure sensing by taking the advantage of inherent physical randomness In particular, PUF unreliability originates from its sensitivity to ambient parameter variations that is usually undesirable for elementary PUF applications—such as authentication and key generation—is exploited to guarantee the veracity of the sensed value In this paper, a PUF naturally acting as a sensor or a PUF explicitly integrated with a sensor is called a PUF sensor Security of sensing in a PUF sensor is attributed to the natural merging of cryptography and sensing to eschew the need for a standalone crypto module Thus, the PUF sensor is appealing for low-cost applications To obtain the sensed value, we develop an authenticated sensing protocol that is robust against eavesdropping, also capable of detecting man-in-the-middle manipulation of the sensed value Compared to initial investigations of PUF sensors, we avoid the stringent requirements of a strong PUF We validate the feasibility of the proposed authenticated sensing protocol based on an experimental implementation of a ring oscillator PUF sensor To improve the sensing capability, we present an efficient approach to select sensitive responses and only employ them for sensing Significantly improved efficacy is validated through comprehensive experimental results

PUF Sensor: Exploiting PUF Unreliability for Secure Wireless Sensing

It is expected that as digital microfluidic biochips (DMFBs) mature, the hardware design flow will begin to resemble the current practice in the semiconductor industry: design teams send chip layouts to third party foundries for fabrication. These foundries are untrusted, and threaten to steal valuable intellectual property (IP). In a DMFB, the IP consists of not only hardware layouts, but also of the biochemical assays (bioassays) that are intended to be executed on-chip. DMFB designers therefore must defend these protocols against theft. We propose to “lock” biochemical assays through random insertion of dummy mix-split operations, subject to several design rules. We experimentally evaluate the proposed locking mechanism, and show how a high level of protection can be achieved even on bioassays with low complexity. We offer guidance on the number of dummy mixsplits required to secure a bioassay for the lifetime of a patent.

Locking of biochemical assays for digital microfluidic biochips

Flow-based microfluidic biochips are revolutionizing biochemical research by automating complex protocols and reducing sample and reagent consumption Integration of these biochips with sensors, actuators, and intelligent control have compounded these benefits while increasing reliability And, many flow-based platforms have successfully transitioned to the marketplace, demonstrating their utility through several recent scientific publications However, these microfluidic technologies and platforms have unintended security and trust implications that threaten their continued success We survey cyberphysical flow-based microfluidic platforms and perform a security assessment We then describe an attack on digital polymerase chain reactions and how such attacks undermine research integrity

Security Implications of Cyberphysical Flow-Based Microfluidic Biochips

Technological shifts in the fields of microfluidics and security are now converging. New techniques in microfluidics increasingly rely on cyberphysical integration and concepts from computer-aided design automation to provide ease-of-use, reliability, and higher throughput. Meanwhile, security concerns are extending beyond traditional information technologies as low-cost computing and sensing proliferates into an ever-increasing number of devices. This keynote paper highlights recent findings and trends in these field to motivate research in the nascent field of cyberphysical microfluidic biochip security and trust.

Toward Secure and Trustworthy Cyberphysical Microfluidic Biochips

We present a micro-electro-mechanical (MEM) relay based physical unclonable function (PUF) that is capable of sensing pressure while providing an assurance of authenticity. The unique properties of the SensorPUF arise from the pressure sensitivity of electrostatically actuated MEM relay structures. Thus, pres sure sensing is made secure by the integration of the sensor reading with the challenge-response generation circuitry. We evaluate the pressure SensorPUF design in terms of uniqueness, diffuseness, uniformity and bit-aliasing while considering the effect of pressure.

Jack Tang

Papers

Secure Randomized Checkpointing for Digital Microfluidic Biochips

Locking of biochemical assays for digital microfluidic biochips

Security Implications of Cyberphysical Flow-Based Microfluidic Biochips

Toward Secure and Trustworthy Cyberphysical Microfluidic Biochips

Securing pressure measurements using SensorPUFs