Willem Gerard Ophey

Robust key extraction from physical uncloneable functions

Physical Uncloneable Functions (PUFs) can be used as a cost-effective means to store key material in an uncloneable way. Due to the fact that the key material is obtained by performing measurements on a physical system, noise is inevitably present in each readout. In this paper we present a number of methods that improve the robustness of bit-string extraction from noisy PUF measurements in general, and in particular for optical PUFs. We describe a practical implementation in the case of optical PUFs and show experimental results.

Information-theoretic security analysis of physical uncloneable functions

We propose a general theoretical framework to analyze the security of Physical Uncloneable Functions (PUFs). We apply the framework to optical PUFs. In particular we present a derivation, based on the physics governing multiple scattering processes, of the number of independent challenge-response pairs supported by a PUF. We find that the number of independent challenge-response pairs is proportional to the square of the thickness of the PUF and inversely proportional to the scattering length and the wavelength of the laser light. We compare our results to those of Pappu and show that they coincide in the case where the density of scatterers becomes very high.Finally, we discuss some attacks on PUFs, and introduce the Slow PUF as a way to thwart brute force attacks.