Korean researchers invent silk-based security device

Researchers from South Korea’s Gwangju Institute of Science have developed a novel digital security device based on natural silk fibres, making it practically unbreachable.

Conventional digital security systems are vulnerable to malicious exploits. One way to address this issue is to use components known as physical unclonable function (PUF) that take advantage of microscopic differences in their makeup to create unique security keys, making them unclonable.

These keys, when read by an electronic device, help to establish or refute the authenticity of the input, thereby either granting or denying access.

Using native silk fibres obtained from silkworms, the research team designed PUF-based tags which were then used to devise a lens-free, optical and portable PUF (LOP-PUF) module.

“When a beam of light hits the disordered silk fibres of an optimal density, it causes light diffraction,” said Young Min Song, senior author and professor at the Gwangju Institute of Science and Technology. “The nanostructures in individual microfibres enhance the contrast of light intensity with respect to the background. The diffracted light is then captured by an image sensor.

“Since the pattern of the micro-holes is naturally made, it is unique, giving rise to a unique pattern of light.”

To achieve the desired intensity and contrast, the researchers optimised the distance between the silk-based PUF and the image sensor. The assembly also included a light-reflecting mirror and three tricolour light-emitting diodes, among other components. Through a series of interventions, the research team processed the captured patterns of light and converted them into a digital format (strings of 0s and 1s).

The results were astounding: the average time required to “fake” the authentication was approximately 5 x 10⁴¹ years, making the LOP-PUF module a practically unbreachable device. Also, the novel security device permitted “digital encryption”, or the conversion of information into a code, to prevent unauthorised access.

“The digital security device we designed is low-cost, portable, eco-friendly, and free of pre- or post-processing,” said Song. “It also does not require a coherent source of light or a bulky lens system. The advantages of this system are manifold.”

The team optimised its LOP-PUF design by making a few tweaks. For example, a cooling fan was added to reduce thermal noise, or the disturbance caused by temperature fluctuations.

“To our knowledge, this is the first PUF module designed using silk – a naturally abundant biomaterial,” said Song. “It means that we don’t need to invest time in developing complicated security keys – nature has already done this for us.”