Silkworms Spin New User Authentication

A group of academics at South Korea’s Gwangju Institute of Science and Technology (GIST) have utilised natural silk fibres from domesticated silkworms to build an environmentally friendly digital security system that they say is ‘practically unbreachable’.

The naturally occurring physical unclonable function (PUF) takes advantage of the diffraction of light through natural micro-holes in natural silk to create a secure and unique digital key for future security solutions.

Physical unclonable functions are devices that leverage inherent randomness and microscopic differences in electronics introduced during manufacturing to generate a unique identifier (eg. cryptographic keys) for a given set of inputs and conditions.

PUFs are not created by algorithms but are one-way functions derived from uncopiable elements to create unbreakable identifiers for strong authentication. Over the years, PUFs have been widely used in smartcards to provide ‘silicon fingerprints’ as a means of uniquely identifying cardholders based on a challenge-response authentication scheme.

The newly proposed method from GIST uses native silk fibres produced by silkworms to create PUF-based tags that are then used to devise a PUF module. This mechanism works on the underlying principle that a light wave experiences diffraction when it hits an obstacle, in this case, the silk fibre, or passes through an aperture – the naturally occurring micro-holes in silk.

‘The nanofibrillar structures in each microfibre significantly improves the light intensity contrast between the background and focal spots owing to the strong scattering,’ the researchers noted in ‘Revisiting silk: a lens-free optical physical unclonable function’ published in Nature Communications ¹. ‘These novel optical features could easily implement the module of a lens-free optical PUF by placing a silk ID card on the image sensor.’

The diffracted light is unique, ‘giving rise to a unique pattern of light,’ that is subsequently converted into a digital format and fed into the system as input, researcher and the study’s author Young Min Song said.

Should such a system be deployed for user authentication using a smart card, the researchers estimate that faking an authentication key generated from the module via a brute-force attack would take as long as 5 x 1041 years to crack it open, making it cryptographically unbreakable. To give perspective, the age of the Solar System is 4.6 x 109 years.

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

1 - https://www.nature.com/articles/s41467-021-27278-5