Pepijn W.H. Pinkse: HgTe as a topological insulator

Modern society strongly relies on secret information for authentication. However, keeping infor­ma­tion secret and accessible is exceedingly difficult in modern society. We have experiment­ally demon­strated Quan­tum-Secure Authentication (QSA) that does not require keeping secret infor­ma­tion but relies on an optical Physical Unclonable Function (PUF) as a key [1]. As illustrated in the figure, we il­lu­mi­nate the key using light containing fewer photons than spatial degrees of freedom. In the key the photons are multiple-scattered by millions of randomly orga­nized nanoparticles. The spatial shape of the re­tur­ned (“res­ponse”) photons depends strongly on the positions of the scatterers and on the in­cident (“challen­ge”) photons. Assuming its challenge-respon­se behavior is known, the key can be authen­ti­cated by illumi­nating it with a challenge and verifying whether the response is as expected. Because of the low photon number, an attacker cannot fully cha­rac­terize the challenge. Therefore, he cannot digitally construct the correct response even if the chal­lenge-response behavior of the key is publicly known. QSA is secure if the physical key is too complex to be copied with current technology, as is believed to be the case for e.g. white paint.