Reconfigurable Complex Photonic Systems for Secure Cryptographic Primitives

Physical Unclonable Functions (PUFs) represent a security primitive that has been introduced two decades ago [1] to obliterate the risks associated with the digital storage of authentication keys. Thanks to their intrinsic structural random disorder and uncontrollable manufacturing variations, a PUF is unique and “unclonable” and can be interrogated following a challenge-response pairs (CRPs) scheme which makes them ideal candidates for non-digital storage of authentication keys. Among the different types of PUFs, optical strong PUFs have been demonstrated as strong photonic materials whose tamper resistance overcomes the attack resilience of their electronic counterpart. However, despite their great potential, the number of Strong Optical PUFs demonstrated so far is still very limited due the material constraints, their response stability and scattering strength [2].<br/>In this scenario, we propose an optically driven reconfigurable strong optical PUFs. By harnessing the light responsive nature of the scattering properties of a dye-doped polymer dispersed liquid crystals (PDLC),we determine the performance of the PUFs in term of stability, and key complexity. The proposed strategy allows to irreversibly reconfigure the scattering potential of the PUF in case of malicious attack. Reconfigurable complex photonic systems thus offer a cheap, reliable and highly entropic media from which cryptographic keys can be extracted on demand for secure authentication protocols based on optical physical functions.<br/><br/><b>References</b><br/>[1] Pappu, R., Recht, B., Taylor, J. and Gershenfeld, N., <i>Physical one-way functions.</i> Science, 297(5589), 2026 (2002).<br/>[2] Gao, Y., Al-Sarawi, S.F. and Abbott, D.,. <i>Physical unclonable functions.</i> Nature Electronics, 3(2), 81 (2020).<br/><br/>The research leading to these results has received funding from AFOSR (grant n° FA9550-21-1-0039) and Ente cassa di Risparmio di Firenze (2017/0881).