According to the team, made up of Min Seok Kim, Gil Ju Lee, Jung Woo Leem, Seungho Choi, Young L. Kim, and Young Min Song, PUFs can act as physical security keys for digital services that cannot be duplicated or cloned.
Hardware security keys, including Yubikey products, provide a physical security barrier for online services. Google, for example, recommends that account holders considered more 'at risk' of attacks use a hardware-based key in order to reduce the likelihood of compromise by requiring another level of authentication.
According to the GIST researchers, future sustainable and eco-friendly authentication keys could be created by taking advantage of the natural, microscopic differences in fiber -- tiny differences that could be used to develop unique, hardware PUFs.
The fibers used to test this idea were obtained from Bombyx mori silkworms. GIST then used an image sensor, light-reflecting mirror, and three light-emitting diodes to capture patterns of light reflected off the silk to create a security tag pattern.
"Randomly distributed fibers in silk generate spatially chaotic diffractions, forming self-focused spots on the millimeter scale," the paper reads. "The silk-based physical unclonable function has a self-focusing, low-cost, and eco-friendly feature without relying on pre-/post-process for security tag creation."
Professor Young Min Song explained that at an "optimal density," a beam of light striking silk causes light diffraction, which is the source of a potential PUF.
"The nanostructures in individual microfibers enhance the contrast of light intensity with respect to the background," Song commented. "The diffracted light is then captured by an image sensor. Since the pattern of the microholes is naturally-made, it is unique, giving rise to a unique pattern of light."
These patterns were then converted into a digital format held in 15 silk "ID cards," of which a reader could then extract an authentication code. When challenged by a basic brute-force attack, the time calculated for bypassing authentication was reported as 5 x 10(41) years.
"To our knowledge, this is the first PUF module designed using silk, a naturally abundant biomaterial," Song added. "It means that we don't need to invest time in developing complicated security keys; nature has already done this for us."